diff --git a/.eslintignore b/.eslintignore
index c1f0da558791..fca8c2651f54 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -220,6 +220,3 @@ tools/tryselect/selectors/chooser/templates/chooser.html
 
 # Ignore preprocessed *(P)refs.js files in update-packaging.
 tools/update-packaging/**/*refs.js
-
-# Ignore backgroundtasks preferences files.
-toolkit/components/backgroundtasks/defaults
diff --git a/.prettierignore b/.prettierignore
index c4b4c32638c9..24fd18b7f33f 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -58,6 +58,3 @@ devtools/client/debugger/src/test/mochitest/examples/ember/quickstart
 
 # These are source mapped and the locations are asserted in the test case.
 devtools/client/webconsole/test/browser/test-mangled-function.*
-
-# Ignore backgroundtasks preferences files.
-toolkit/components/backgroundtasks/defaults
diff --git a/browser/installer/Makefile.in b/browser/installer/Makefile.in
index ad725c5114b0..b861ad214a64 100644
--- a/browser/installer/Makefile.in
+++ b/browser/installer/Makefile.in
@@ -98,10 +98,6 @@ ifdef MOZ_DEFAULT_BROWSER_AGENT
 DEFINES += -DMOZ_DEFAULT_BROWSER_AGENT=1
 endif
 
-ifdef MOZ_BACKGROUNDTASKS
-DEFINES += -DMOZ_BACKGROUNDTASKS=1
-endif
-
 ifeq (cocoa,$(MOZ_WIDGET_TOOLKIT))
 MOZ_PKG_MAC_DSSTORE=$(topsrcdir)/$(MOZ_BRANDING_DIRECTORY)/dsstore
 MOZ_PKG_MAC_BACKGROUND=$(topsrcdir)/$(MOZ_BRANDING_DIRECTORY)/background.png
diff --git a/browser/installer/package-manifest.in b/browser/installer/package-manifest.in
index ec20499166e8..f060c457cee2 100644
--- a/browser/installer/package-manifest.in
+++ b/browser/installer/package-manifest.in
@@ -305,12 +305,6 @@
 ; gre location for now.
 @RESPATH@/defaults/pref/channel-prefs.js
 
-; Background tasks-specific preferences.  These are in the GRE
-; location since they apply to all tasks at this time.
-#ifdef MOZ_BACKGROUNDTASKS
-@RESPATH@/defaults/backgroundtasks/backgroundtasks.js
-#endif
-
 ; [Layout Engine Resources]
 ; Style Sheets, Graphics and other Resources used by the layout engine.
 @RESPATH@/res/EditorOverride.css
diff --git a/extensions/pref/autoconfig/src/components.conf b/extensions/pref/autoconfig/src/components.conf
index 41de3526948d..789a44b2e39b 100644
--- a/extensions/pref/autoconfig/src/components.conf
+++ b/extensions/pref/autoconfig/src/components.conf
@@ -11,11 +11,6 @@ Classes = [
         'type': 'nsReadConfig',
         'headers': ['/extensions/pref/autoconfig/src/nsReadConfig.h'],
         'init_method': 'Init',
-        'categories': {
-            'pref-config-startup': {
-                'name': 'ReadConfig Module',
-                'backgroundtasks': BackgroundTasksSelector.ALL_TASKS,
-            },
-        },
+        'categories': {'pref-config-startup': 'ReadConfig Module'},
     },
 ]
diff --git a/layout/build/components.conf b/layout/build/components.conf
index 0b93693449b4..a89a73930172 100644
--- a/layout/build/components.conf
+++ b/layout/build/components.conf
@@ -96,12 +96,7 @@ Classes = [
         'cid': '{fc886801-e768-11d4-9885-00c04fa0cf4b}',
         'contract_ids': ['@mozilla.org/content/document-loader-factory;1'],
         'type': 'nsIDocumentLoaderFactory',
-        'categories': {
-            'Gecko-Content-Viewers': {
-                'name': content_types,
-                'backgroundtasks': BackgroundTasksSelector.ALL_TASKS,
-            }
-        },
+        'categories': {'Gecko-Content-Viewers': content_types},
     },
     {
         'cid': '{0ddf4df8-4dbb-4133-8b79-9afb966514f5}',
@@ -294,14 +289,8 @@ Classes = [
         'type': 'nsMixedContentBlocker',
         'headers': ['mozilla/dom/nsMixedContentBlocker.h'],
         'categories': {
-            'content-policy': {
-                'name': '@mozilla.org/mixedcontentblocker;1',
-                'backgroundtasks': BackgroundTasksSelector.ALL_TASKS,
-            },
-            'net-channel-event-sinks': {
-                'name': '@mozilla.org/mixedcontentblocker;1',
-                'backgroundtasks': BackgroundTasksSelector.ALL_TASKS,
-            },
+            'content-policy': '@mozilla.org/mixedcontentblocker;1',
+            'net-channel-event-sinks': '@mozilla.org/mixedcontentblocker;1',
         },
     },
     {
diff --git a/modules/libpref/Preferences.cpp b/modules/libpref/Preferences.cpp
index 2a7f5bacbd83..cfc498d5c250 100644
--- a/modules/libpref/Preferences.cpp
+++ b/modules/libpref/Preferences.cpp
@@ -86,9 +86,6 @@
 #include "plstr.h"
 #include "prlink.h"
 #include "xpcpublic.h"
-#ifdef MOZ_BACKGROUNDTASKS
-#  include "mozilla/BackgroundTasks.h"
-#endif
 
 #ifdef DEBUG
 #  include <map>
@@ -4533,13 +4530,6 @@ nsresult Preferences::InitInitialObjects(bool aIsStartup) {
     rv = pref_ReadDefaultPrefs(jarReader, "defaults/pref/*.js$");
     NS_ENSURE_SUCCESS(rv, rv);
 
-#ifdef MOZ_BACKGROUNDTASKS
-    if (BackgroundTasks::IsBackgroundTaskMode()) {
-      rv = pref_ReadDefaultPrefs(jarReader, "defaults/backgroundtasks/*.js$");
-      NS_ENSURE_SUCCESS(rv, rv);
-    }
-#endif
-
 #ifdef MOZ_WIDGET_ANDROID
     // Load jar:$gre/omni.jar!/defaults/pref/$MOZ_ANDROID_CPU_ABI/*.js.
     nsAutoCString path;
@@ -4619,25 +4609,6 @@ nsresult Preferences::InitInitialObjects(bool aIsStartup) {
         NS_WARNING("Error parsing preferences.");
       }
     }
-
-#ifdef MOZ_BACKGROUNDTASKS
-    if (BackgroundTasks::IsBackgroundTaskMode()) {
-      rv = appJarReader->FindInit("defaults/backgroundtasks/*.js$",
-                                  getter_Transfers(find));
-      NS_ENSURE_SUCCESS(rv, rv);
-      prefEntries.Clear();
-      while (NS_SUCCEEDED(find->FindNext(&entryName, &entryNameLen))) {
-        prefEntries.AppendElement(Substring(entryName, entryNameLen));
-      }
-      prefEntries.Sort();
-      for (uint32_t i = prefEntries.Length(); i--;) {
-        rv = pref_ReadPrefFromJar(appJarReader, prefEntries[i].get());
-        if (NS_FAILED(rv)) {
-          NS_WARNING("Error parsing preferences.");
-        }
-      }
-    }
-#endif
   }
 
   nsCOMPtr<nsIProperties> dirSvc(
diff --git a/modules/libpref/moz.build b/modules/libpref/moz.build
index d0ccfcff6609..9273ab29dc99 100644
--- a/modules/libpref/moz.build
+++ b/modules/libpref/moz.build
@@ -167,6 +167,3 @@ else:
     FINAL_TARGET_PP_FILES += [
         "greprefs.js",
     ]
-
-if CONFIG["MOZ_BACKGROUNDTASKS"]:
-    DEFINES["MOZ_BACKGROUNDTASKS"] = True
diff --git a/startupcache/StartupCache.cpp b/startupcache/StartupCache.cpp
index 81a922a815d3..29832ae42f4b 100644
--- a/startupcache/StartupCache.cpp
+++ b/startupcache/StartupCache.cpp
@@ -35,9 +35,6 @@
 #include "GeckoProfiler.h"
 #include "nsAppRunner.h"
 #include "xpcpublic.h"
-#ifdef MOZ_BACKGROUNDTASKS
-#  include "mozilla/BackgroundTasks.h"
-#endif
 
 #if defined(XP_WIN)
 #  include <windows.h>
@@ -118,12 +115,6 @@ StartupCache* StartupCache::GetSingletonNoInit() {
 }
 
 StartupCache* StartupCache::GetSingleton() {
-#ifdef MOZ_BACKGROUNDTASKS
-  if (BackgroundTasks::IsBackgroundTaskMode()) {
-    return nullptr;
-  }
-#endif
-
   if (!gStartupCache) {
     if (!XRE_IsParentProcess()) {
       return nullptr;
diff --git a/startupcache/moz.build b/startupcache/moz.build
index 37b8d4785f88..a05aebd47299 100644
--- a/startupcache/moz.build
+++ b/startupcache/moz.build
@@ -31,7 +31,4 @@ XPIDL_SOURCES += [
     "nsIStartupCacheInfo.idl",
 ]
 
-if CONFIG["MOZ_BACKGROUNDTASKS"]:
-    DEFINES["MOZ_BACKGROUNDTASKS"] = True
-
 FINAL_LIBRARY = "xul"
diff --git a/toolkit/components/backgroundtasks/BackgroundTask_exception.jsm b/toolkit/components/backgroundtasks/BackgroundTask_exception.jsm
deleted file mode 100644
index 0e7de4b9210e..000000000000
--- a/toolkit/components/backgroundtasks/BackgroundTask_exception.jsm
+++ /dev/null
@@ -1,12 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-var EXPORTED_SYMBOLS = ["runBackgroundTask"];
-
-async function runBackgroundTask() {
-  console.error("runBackgroundTask: exception");
-
-  throw new Error("test");
-}
diff --git a/toolkit/components/backgroundtasks/BackgroundTask_failure.jsm b/toolkit/components/backgroundtasks/BackgroundTask_failure.jsm
deleted file mode 100644
index 553d8cedb2a0..000000000000
--- a/toolkit/components/backgroundtasks/BackgroundTask_failure.jsm
+++ /dev/null
@@ -1,12 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-var EXPORTED_SYMBOLS = ["runBackgroundTask"];
-
-async function runBackgroundTask() {
-  console.error("runBackgroundTask: failure");
-
-  return 1;
-}
diff --git a/toolkit/components/backgroundtasks/BackgroundTask_success.jsm b/toolkit/components/backgroundtasks/BackgroundTask_success.jsm
deleted file mode 100644
index e64612c2bb99..000000000000
--- a/toolkit/components/backgroundtasks/BackgroundTask_success.jsm
+++ /dev/null
@@ -1,12 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-var EXPORTED_SYMBOLS = ["runBackgroundTask"];
-
-async function runBackgroundTask() {
-  console.error("runBackgroundTask: success");
-
-  return 0;
-}
diff --git a/toolkit/components/backgroundtasks/BackgroundTasks.h b/toolkit/components/backgroundtasks/BackgroundTasks.h
index 3a2d13cc6231..f3cdc50962e7 100644
--- a/toolkit/components/backgroundtasks/BackgroundTasks.h
+++ b/toolkit/components/backgroundtasks/BackgroundTasks.h
@@ -8,11 +8,9 @@
 
 #include "nsCOMPtr.h"
 #include "nsIBackgroundTasks.h"
-#include "nsIBackgroundTasksManager.h"
 #include "nsICommandLine.h"
 #include "nsIFile.h"
 #include "nsISupports.h"
-#include "nsImportModule.h"
 #include "nsString.h"
 #include "nsXULAppAPI.h"
 
@@ -113,14 +111,7 @@ class BackgroundTasks final : public nsIBackgroundTasks {
       return NS_ERROR_NOT_AVAILABLE;
     }
 
-    nsCOMPtr<nsIBackgroundTasksManager> manager =
-        do_ImportModule("resource://gre/modules/BackgroundTasksManager.jsm",
-                        "BackgroundTasksManager");
-
-    NS_ENSURE_TRUE(manager, NS_ERROR_FAILURE);
-
-    NS_ConvertASCIItoUTF16 name(task.ref().get());
-    Unused << manager->RunBackgroundTaskNamed(name, aCmdLine);
+    // For now, do nothing.
 
     return NS_OK;
   }
diff --git a/toolkit/components/backgroundtasks/BackgroundTasksManager.jsm b/toolkit/components/backgroundtasks/BackgroundTasksManager.jsm
deleted file mode 100644
index fa5d644a1ae7..000000000000
--- a/toolkit/components/backgroundtasks/BackgroundTasksManager.jsm
+++ /dev/null
@@ -1,134 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-var EXPORTED_SYMBOLS = ["BackgroundTasksManager"];
-
-const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
-const { XPCOMUtils } = ChromeUtils.import(
-  "resource://gre/modules/XPCOMUtils.jsm"
-);
-
-XPCOMUtils.defineLazyGetter(this, "log", () => {
-  let ConsoleAPI = ChromeUtils.import("resource://gre/modules/Console.jsm", {})
-    .ConsoleAPI;
-  let consoleOptions = {
-    // tip: set maxLogLevel to "debug" and use log.debug() to create detailed
-    // messages during development. See LOG_LEVELS in Console.jsm for details.
-    maxLogLevel: "error",
-    maxLogLevelPref: "toolkit.backgroundtasks.loglevel",
-    prefix: "BackgroundTasksManager",
-  };
-  return new ConsoleAPI(consoleOptions);
-});
-
-// Map resource://testing-common/ to the shared test modules directory.  This is
-// a transliteration of `register_modules_protocol_handler` from
-// https://searchfox.org/mozilla-central/rev/f081504642a115cb8236bea4d8250e5cb0f39b02/testing/xpcshell/head.js#358-389.
-function registerModulesProtocolHandler() {
-  let env = Cc["@mozilla.org/process/environment;1"].getService(
-    Ci.nsIEnvironment
-  );
-  let _TESTING_MODULES_URI = env.get("XPCSHELL_TESTING_MODULES_URI", "");
-  if (!_TESTING_MODULES_URI) {
-    return false;
-  }
-
-  let protocolHandler = Services.io
-    .getProtocolHandler("resource")
-    .QueryInterface(Ci.nsIResProtocolHandler);
-
-  protocolHandler.setSubstitution(
-    "testing-common",
-    Services.io.newURI(_TESTING_MODULES_URI)
-  );
-  // Log loudly so that when testing, we always actually use the
-  // console logging mechanism and therefore deterministically load that code.
-  log.error(
-    `Substitution set: resource://testing-common aliases ${_TESTING_MODULES_URI}`
-  );
-
-  return true;
-}
-
-/**
- * Find a JSM named like `backgroundtasks/BackgroundTask_${name}.jsm`
- * and return its `runBackgroundTask` function.
- *
- * When testing, allow to load from `XPCSHELL_TESTING_MODULES_URI`,
- * which is registered at `resource://testing-common`, the standard
- * location for test-only modules.
- *
- * @return {function} `runBackgroundTask` function.
- * @throws NS_ERROR_NOT_AVAILABLE if a background task with the given `name` is
- * not found.
- */
-function findRunBackgroundTask(name) {
-  const subModules = [
-    "resource:///modules", // App-specific first.
-    "resource://gre/modules", // Toolkit/general second.
-  ];
-
-  if (registerModulesProtocolHandler()) {
-    subModules.push("resource://testing-common"); // Test-only third.
-  }
-
-  for (const subModule of subModules) {
-    let URI = `${subModule}/backgroundtasks/BackgroundTask_${name}.jsm`;
-    log.debug(`Looking for background task at URI: ${URI}`);
-
-    try {
-      const { runBackgroundTask } = ChromeUtils.import(URI);
-      log.info(`Found background task at URI: ${URI}`);
-      return runBackgroundTask;
-    } catch (ex) {
-      if (ex.result != Cr.NS_ERROR_FILE_NOT_FOUND) {
-        throw ex;
-      }
-    }
-  }
-
-  log.warn(`No backgroundtask named '${name}' registered`);
-  throw new Components.Exception(
-    `No backgroundtask named '${name}' registered`,
-    Cr.NS_ERROR_NOT_AVAILABLE
-  );
-}
-
-var BackgroundTasksManager = {
-  async runBackgroundTaskNamed(name, commandLine) {
-    function addMarker(markerName) {
-      return ChromeUtils.addProfilerMarker(markerName, undefined, name);
-    }
-    addMarker("BackgroundTasksManager:AfterRunBackgroundTaskNamed");
-
-    log.info(
-      `Running background task named '${name}' (with ${commandLine.length} arguments)`
-    );
-
-    let exitCode = 2;
-    try {
-      let runBackgroundTask = findRunBackgroundTask(name);
-      addMarker("BackgroundTasksManager:AfterFindRunBackgroundTask");
-
-      try {
-        // TODO: timeout tasks that run too long.
-        exitCode = await runBackgroundTask(commandLine);
-        log.info(
-          `Backgroundtask named '${name}' completed with exit code ${exitCode}`
-        );
-      } catch (e) {
-        log.error(`Backgroundtask named '${name}' threw exception`, e);
-        exitCode = 3;
-      }
-    } finally {
-      addMarker("BackgroundTasksManager:AfterAwaitRunBackgroundTask");
-
-      log.info(`Invoking Services.startup.quit(..., ${exitCode})`);
-      Services.startup.quit(Ci.nsIAppStartup.eForceQuit, exitCode);
-    }
-
-    return exitCode;
-  },
-};
diff --git a/toolkit/components/backgroundtasks/defaults/backgroundtasks.js b/toolkit/components/backgroundtasks/defaults/backgroundtasks.js
deleted file mode 100644
index a52c1b117873..000000000000
--- a/toolkit/components/backgroundtasks/defaults/backgroundtasks.js
+++ /dev/null
@@ -1,27 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-pref("browser.dom.window.dump.enabled", true);
-pref("devtools.console.stdout.chrome", true);
-
-pref("network.process.enabled", false);
-
-pref("toolkit.telemetry.archive.enabled", false);
-pref("toolkit.telemetry.firstShutdownPing.enabled", false);
-pref("toolkit.telemetry.healthping.enabled", false);
-pref("toolkit.telemetry.newProfilePing.enabled", false);
-pref("toolkit.telemetry.eventping.enabled", false);
-pref("toolkit.telemetry.ecosystemtelemetry.enabled", false);
-pref("toolkit.telemetry.prioping.enabled", false);
-pref("datareporting.policy.dataSubmissionEnabled", false);
-pref("datareporting.healthreport.uploadEnabled", false);
-
-pref("browser.cache.offline.enable", false);
-pref("browser.cache.offline.storage.enable", false);
-pref("browser.cache.disk.enable", false);
-pref("permissions.memory_only", true);
-
-// For testing only: used to test that backgroundtask-specific prefs are
-// processed.  This just needs to be an unusual integer in the range 0..127.
-pref("test.backgroundtask_specific_pref.exitCode", 79);
diff --git a/toolkit/components/backgroundtasks/moz.build b/toolkit/components/backgroundtasks/moz.build
index 1e2b13731ad7..184b1b4a018a 100644
--- a/toolkit/components/backgroundtasks/moz.build
+++ b/toolkit/components/backgroundtasks/moz.build
@@ -22,31 +22,8 @@ XPCOM_MANIFESTS += [
 
 XPIDL_SOURCES += [
     "nsIBackgroundTasks.idl",
-    "nsIBackgroundTasksManager.idl",
 ]
 
 XPIDL_MODULE = "toolkit_backgroundtasks"
 
-EXTRA_JS_MODULES += [
-    "BackgroundTasksManager.jsm",
-]
-
-EXTRA_JS_MODULES.backgroundtasks += [
-    "BackgroundTask_exception.jsm",
-    "BackgroundTask_failure.jsm",
-    "BackgroundTask_success.jsm",
-]
-
-BROWSER_CHROME_MANIFESTS += ["tests/browser/browser.ini"]
 XPCSHELL_TESTS_MANIFESTS += ["tests/xpcshell/xpcshell.ini"]
-
-TESTING_JS_MODULES.backgroundtasks += [
-    "tests/BackgroundTask_backgroundtask_specific_pref.jsm",
-    "tests/BackgroundTask_crash.jsm",
-    "tests/BackgroundTask_policies.jsm",
-    "tests/BackgroundTask_wait.jsm",
-]
-
-FINAL_TARGET_FILES.defaults.backgroundtasks += [
-    "defaults/backgroundtasks.js",
-]
diff --git a/toolkit/components/backgroundtasks/nsIBackgroundTasksManager.idl b/toolkit/components/backgroundtasks/nsIBackgroundTasksManager.idl
deleted file mode 100644
index 0bf6ded3698f..000000000000
--- a/toolkit/components/backgroundtasks/nsIBackgroundTasksManager.idl
+++ /dev/null
@@ -1,28 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "nsISupports.idl"
-
-interface nsICommandLine;
-
-/**
- * Import and run named backgroundtask implementations.
- */
-[scriptable, function, uuid(4d48c536-e16f-4699-8f9c-add4f28f92f0)]
-interface nsIBackgroundTasksManager : nsISupports
-{
-  /**
-   * Run the named background task.
-   *
-   * @param aTaskName the name of the task to be run.
-   * @param aCommandLine the command line of this invocation.
-   *
-   * This returns a promise which resolves to an integer exit code, 0 when the
-   * task succeeded, >0 otherwise.  The task manager will quit after this
-   * promise resolves.
-   */
-  void runBackgroundTaskNamed(in AString aTaskName,
-                              in nsICommandLine aCommandLine);
-};
diff --git a/toolkit/components/backgroundtasks/tests/BackgroundTask_backgroundtask_specific_pref.jsm b/toolkit/components/backgroundtasks/tests/BackgroundTask_backgroundtask_specific_pref.jsm
deleted file mode 100644
index 0fa900f04f5e..000000000000
--- a/toolkit/components/backgroundtasks/tests/BackgroundTask_backgroundtask_specific_pref.jsm
+++ /dev/null
@@ -1,23 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-var EXPORTED_SYMBOLS = ["runBackgroundTask"];
-
-const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
-
-async function runBackgroundTask(commandLine) {
-  let pref = commandLine.length
-    ? commandLine.getArgument(0)
-    : "test.backgroundtask_specific_pref.exitCode";
-
-  // 0, 1, 2, 3 are all meaningful exit codes already.
-  let exitCode = Services.prefs.getIntPref(pref, 4);
-
-  console.error(
-    `runBackgroundTask: backgroundtask_specific_pref read pref '${pref}', exiting with exitCode ${exitCode}`
-  );
-
-  return exitCode;
-}
diff --git a/toolkit/components/backgroundtasks/tests/BackgroundTask_crash.jsm b/toolkit/components/backgroundtasks/tests/BackgroundTask_crash.jsm
deleted file mode 100644
index b3d7c25705c0..000000000000
--- a/toolkit/components/backgroundtasks/tests/BackgroundTask_crash.jsm
+++ /dev/null
@@ -1,56 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-var EXPORTED_SYMBOLS = ["runBackgroundTask"];
-
-const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
-
-async function runBackgroundTask(commandLine) {
-  // This task depends on `CrashTestUtils.jsm` and requires the
-  // sibling `testcrasher` library to be in the current working
-  // directory.  Fail right away if we can't find the module or the
-  // native library.
-  let testPath = Services.dirsvc.get("CurWorkD", Ci.nsIFile).path;
-  const { CrashTestUtils } = ChromeUtils.import(
-    `file://${testPath}/CrashTestUtils.jsm`
-  );
-
-  // Get the temp dir.
-  var env = Cc["@mozilla.org/process/environment;1"].getService(
-    Ci.nsIEnvironment
-  );
-  var tmpd = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
-  tmpd.initWithPath(env.get("XPCSHELL_TEST_TEMP_DIR"));
-
-  var crashReporter = Cc["@mozilla.org/toolkit/crash-reporter;1"].getService(
-    Ci.nsICrashReporter
-  );
-
-  // We need to call this or crash events go in an undefined location.
-  crashReporter.UpdateCrashEventsDir();
-
-  // Setting the minidump path is not allowed in content processes,
-  // but background tasks run in the parent.
-  crashReporter.minidumpPath = tmpd;
-
-  // Arguments are [crashType, key1, value1, key2, value2, ...].
-  let i = 0;
-  let crashType = Number.parseInt(commandLine.getArgument(i));
-  i += 1;
-  while (i + 1 < commandLine.length) {
-    let key = commandLine.getArgument(i);
-    let value = commandLine.getArgument(i + 1);
-    i += 2;
-    crashReporter.annotateCrashReport(key, value);
-  }
-
-  console.log(`Crashing with crash type ${crashType}`);
-
-  // Now actually crash.
-  CrashTestUtils.crash(crashType);
-
-  // This is moot, since we crashed, but...
-  return 1;
-}
diff --git a/toolkit/components/backgroundtasks/tests/BackgroundTask_policies.jsm b/toolkit/components/backgroundtasks/tests/BackgroundTask_policies.jsm
deleted file mode 100644
index 50261549766d..000000000000
--- a/toolkit/components/backgroundtasks/tests/BackgroundTask_policies.jsm
+++ /dev/null
@@ -1,31 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-var EXPORTED_SYMBOLS = ["runBackgroundTask"];
-
-const { Checker } = ChromeUtils.import(
-  "resource://gre/modules/UpdateService.jsm"
-);
-const { EnterprisePolicyTesting } = ChromeUtils.import(
-  "resource://testing-common/EnterprisePolicyTesting.jsm"
-);
-
-async function runBackgroundTask(commandLine) {
-  let filePath = commandLine.getArgument(0);
-  await EnterprisePolicyTesting.setupPolicyEngineWithJson(filePath);
-
-  let checker = new Checker();
-  let actual = await checker.getUpdateURL();
-  let expected = commandLine.getArgument(1);
-
-  // 0, 1, 2, 3 are all meaningful exit codes already.
-  let exitCode = expected == actual ? 0 : 4;
-  console.error(
-    `runBackgroundTask: policies read AppUpdateURL '${actual}',
-     expected '${expected}', exiting with exitCode ${exitCode}`
-  );
-
-  return exitCode;
-}
diff --git a/toolkit/components/backgroundtasks/tests/BackgroundTask_wait.jsm b/toolkit/components/backgroundtasks/tests/BackgroundTask_wait.jsm
deleted file mode 100644
index b629cbe1ad60..000000000000
--- a/toolkit/components/backgroundtasks/tests/BackgroundTask_wait.jsm
+++ /dev/null
@@ -1,19 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-var EXPORTED_SYMBOLS = ["runBackgroundTask"];
-
-const { setTimeout } = ChromeUtils.import("resource://gre/modules/Timer.jsm");
-
-function runBackgroundTask(commandLine) {
-  let delay = 10;
-  if (commandLine.length) {
-    delay = Number.parseInt(commandLine.getArgument(0));
-  }
-
-  console.error(`runBackgroundTask: wait ${delay} seconds`);
-
-  return new Promise(resolve => setTimeout(resolve, delay * 1000));
-}
diff --git a/toolkit/components/backgroundtasks/tests/browser/browser.ini b/toolkit/components/backgroundtasks/tests/browser/browser.ini
deleted file mode 100644
index 1524d431b499..000000000000
--- a/toolkit/components/backgroundtasks/tests/browser/browser.ini
+++ /dev/null
@@ -1,11 +0,0 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-[DEFAULT]
-skip-if = toolkit == 'android'
-head = head.js
-
-[browser_backgroundtask_specific_pref.js]
-[browser_xpcom_graph_wait.js]
-skip-if = tsan # TSan times out on pretty much all profiler-consuming tests.
diff --git a/toolkit/components/backgroundtasks/tests/browser/browser_backgroundtask_specific_pref.js b/toolkit/components/backgroundtasks/tests/browser/browser_backgroundtask_specific_pref.js
deleted file mode 100644
index b80ee2f59376..000000000000
--- a/toolkit/components/backgroundtasks/tests/browser/browser_backgroundtask_specific_pref.js
+++ /dev/null
@@ -1,23 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * vim: sw=4 ts=4 sts=4 et
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-add_task(async function test_backgroundtask_specific_pref() {
-  // First, verify this pref isn't set in Gecko itself.
-  Assert.equal(
-    -1,
-    Services.prefs.getIntPref("test.backgroundtask_specific_pref.exitCode", -1)
-  );
-
-  // Second, verify that this pref is set in background tasks.
-  // mochitest-chrome tests locally test both unpackaged and packaged
-  // builds (with `--appname=dist`).
-  let exitCode = await do_backgroundtask("backgroundtask_specific_pref", {
-    extraArgs: ["test.backgroundtask_specific_pref.exitCode"],
-  });
-  Assert.equal(79, exitCode);
-});
diff --git a/toolkit/components/backgroundtasks/tests/browser/browser_xpcom_graph_wait.js b/toolkit/components/backgroundtasks/tests/browser/browser_xpcom_graph_wait.js
deleted file mode 100644
index 16a09044130c..000000000000
--- a/toolkit/components/backgroundtasks/tests/browser/browser_xpcom_graph_wait.js
+++ /dev/null
@@ -1,450 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * vim: sw=4 ts=4 sts=4 et
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-/* This test records code loaded during a dummy background task.
- *
- * To run this test similar to try server, you need to run:
- *   ./mach package
- *   ./mach test --appname=dist <path to test>
- *
- * If you made changes that cause this test to fail, it's likely
- * because you are changing the application startup process.  In
- * general, you should prefer to defer loading code as long as you
- * can, especially if it's not going to be used in background tasks.
- */
-
-"use strict";
-
-const { OS } = ChromeUtils.import("resource://gre/modules/osfile.jsm");
-
-const Cm = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
-
-// Shortcuts for conditions.
-const LINUX = AppConstants.platform == "linux";
-const WIN = AppConstants.platform == "win";
-const MAC = AppConstants.platform == "macosx";
-
-const backgroundtaskPhases = {
-  AfterRunBackgroundTaskNamed: {
-    allowlist: {
-      components: [], // At this time, no phase loads a JS component.
-      modules: [
-        "resource://gre/modules/AppConstants.jsm",
-        "resource://gre/modules/AsyncShutdown.jsm",
-        "resource://gre/modules/BackgroundTasksManager.jsm",
-        {
-          name: "resource://gre/modules/Console.jsm",
-          condition: WIN,
-        },
-        "resource://gre/modules/EnterprisePolicies.jsm",
-        "resource://gre/modules/EnterprisePoliciesParent.jsm",
-        "resource://gre/modules/PromiseUtils.jsm",
-        "resource://gre/modules/Services.jsm",
-        "resource://gre/modules/XPCOMUtils.jsm",
-        "resource://gre/modules/nsAsyncShutdown.jsm",
-      ],
-      // Human-readable contract IDs are many-to-one mapped to CIDs, so this
-      // list is a little misleading.  For example, all of
-      // "@mozilla.org/xre/app-info;1", "@mozilla.org/xre/runtime;1", and
-      // "@mozilla.org/toolkit/crash-reporter;1", map to the CID
-      // {95d89e3e-a169-41a3-8e56-719978e15b12}, but only one is listed here.
-      // We could be more precise by listing CIDs, but that's a good deal harder
-      // to read and modify.
-      services: [
-        "@mozilla.org/async-shutdown-service;1",
-        "@mozilla.org/base/telemetry;1",
-        "@mozilla.org/categorymanager;1",
-        "@mozilla.org/chrome/chrome-registry;1",
-        "@mozilla.org/cookieService;1",
-        "@mozilla.org/docloaderservice;1",
-        "@mozilla.org/embedcomp/window-watcher;1",
-        "@mozilla.org/enterprisepolicies;1",
-        "@mozilla.org/file/directory_service;1",
-        "@mozilla.org/intl/stringbundle;1",
-        "@mozilla.org/layout/content-policy;1",
-        "@mozilla.org/memory-reporter-manager;1",
-        "@mozilla.org/network/captive-portal-service;1",
-        "@mozilla.org/network/effective-tld-service;1",
-        "@mozilla.org/network/idn-service;1",
-        "@mozilla.org/network/io-service;1",
-        "@mozilla.org/network/network-link-service;1",
-        "@mozilla.org/network/protocol;1?name=chrome",
-        "@mozilla.org/network/protocol;1?name=file",
-        "@mozilla.org/network/protocol;1?name=jar",
-        "@mozilla.org/network/protocol;1?name=resource",
-        "@mozilla.org/network/socket-transport-service;1",
-        "@mozilla.org/network/stream-transport-service;1",
-        "@mozilla.org/network/url-parser;1?auth=maybe",
-        "@mozilla.org/network/url-parser;1?auth=no",
-        "@mozilla.org/network/url-parser;1?auth=yes",
-        "@mozilla.org/observer-service;1",
-        "@mozilla.org/permissionmanager;1",
-        "@mozilla.org/power/powermanagerservice;1",
-        "@mozilla.org/preferences-service;1",
-        "@mozilla.org/process/environment;1",
-        "@mozilla.org/storage/service;1",
-        "@mozilla.org/thirdpartyutil;1",
-        "@mozilla.org/toolkit/app-startup;1",
-        "@mozilla.org/toolkit/profile-service;1",
-        "@mozilla.org/uuid-generator;1",
-        {
-          name: "@mozilla.org/widget/appshell/mac;1",
-          condition: MAC,
-        },
-        {
-          name: "@mozilla.org/widget/appshell/gtk;1",
-          condition: LINUX,
-        },
-        {
-          name: "@mozilla.org/widget/appshell/win;1",
-          condition: WIN,
-        },
-        "@mozilla.org/xpcom/debug;1",
-        "@mozilla.org/xre/app-info;1",
-      ],
-    },
-  },
-  AfterFindRunBackgroundTask: {
-    allowlist: {
-      components: [],
-      modules: [
-        // We have a profile marker for this, even though it failed to load!
-        "resource:///modules/backgroundtasks/BackgroundTask_wait.jsm",
-        {
-          name: "resource://gre/modules/Console.jsm",
-          condition: !WIN,
-        },
-        "resource://gre/modules/ConsoleAPIStorage.jsm",
-        "resource://gre/modules/Timer.jsm",
-        // We have a profile marker for this, even though it failed to load!
-        "resource://gre/modules/backgroundtasks/BackgroundTask_wait.jsm",
-        "resource://testing-common/backgroundtasks/BackgroundTask_wait.jsm",
-      ],
-      services: ["@mozilla.org/consoleAPI-storage;1"],
-    },
-  },
-  AfterAwaitRunBackgroundTask: {
-    allowlist: {
-      components: [],
-      modules: [],
-      services: [
-        "@mozilla.org/network/protocol/about;1?what=preferences",
-        "@mozilla.org/network/protocol;1?name=about",
-        "@mozilla.org/network/protocol;1?name=http",
-        "@mozilla.org/network/protocol;1?name=https",
-      ],
-    },
-  },
-};
-
-function getStackFromProfile(profile, stack, libs) {
-  const stackPrefixCol = profile.stackTable.schema.prefix;
-  const stackFrameCol = profile.stackTable.schema.frame;
-  const frameLocationCol = profile.frameTable.schema.location;
-
-  let index = 1;
-  let result = [];
-  while (stack) {
-    let sp = profile.stackTable.data[stack];
-    let frame = profile.frameTable.data[sp[stackFrameCol]];
-    stack = sp[stackPrefixCol];
-    frame = profile.stringTable[frame[frameLocationCol]];
-
-    if (frame.startsWith("0x")) {
-      try {
-        let addr = frame.slice("0x".length);
-        addr = Number.parseInt(addr, 16);
-        for (let lib of libs) {
-          if (lib.start <= addr && addr <= lib.end) {
-            // Only handle two digits for now.
-            let indexString = index.toString(10);
-            if (indexString.length == 1) {
-              indexString = "0" + indexString;
-            }
-            let offset = addr - lib.start;
-            frame = `#${indexString}: ???[${lib.debugPath} ${"+0x" +
-              offset.toString(16)}]`;
-            break;
-          }
-        }
-      } catch (e) {
-        // Fall through.
-      }
-    }
-
-    if (frame != "js::RunScript" && !frame.startsWith("next (self-hosted:")) {
-      result.push(frame);
-      index += 1;
-    }
-  }
-  return result;
-}
-
-add_task(async function test_xpcom_graph_wait() {
-  {
-    let omniJa = Services.dirsvc.get("XCurProcD", Ci.nsIFile);
-    omniJa.append("omni.ja");
-    if (!omniJa.exists()) {
-      ok(
-        false,
-        "This test requires a packaged build, " +
-          "run 'mach package' and then use --appname=dist"
-      );
-      return;
-    }
-  }
-
-  let profilePath = Cc["@mozilla.org/process/environment;1"]
-    .getService(Ci.nsIEnvironment)
-    .get("MOZ_UPLOAD_DIR");
-  profilePath =
-    profilePath ||
-    FileUtils.getDir("ProfD", [`testBackgroundTask-${Math.random()}`], true)
-      .path;
-
-  profilePath = OS.Path.join(profilePath, "profile_backgroundtask_wait.json");
-  await IOUtils.remove(profilePath, { ignoreAbsent: true });
-
-  let extraEnv = {
-    MOZ_PROFILER_STARTUP: "1",
-    MOZ_PROFILER_SHUTDOWN: profilePath,
-  };
-
-  let exitCode = await do_backgroundtask("wait", { extraEnv });
-  Assert.equal(0, exitCode);
-
-  let fileContents = await IOUtils.readUTF8(profilePath);
-  let rootProfile = JSON.parse(fileContents);
-  let profile = rootProfile.threads[0];
-
-  const nameCol = profile.markers.schema.name;
-  const dataCol = profile.markers.schema.data;
-
-  function newMarkers() {
-    return {
-      components: [], // The equivalent of `Cu.loadedComponents`.
-      modules: [], // The equivalent of `Cu.loadedModules`.
-      services: [],
-    };
-  }
-
-  let phases = {};
-  let markersForCurrentPhase = newMarkers();
-
-  // If a subsequent phase loads an already loaded resource, that's
-  // fine.  Track all loaded resources to ignore such repeated loads.
-  let markersForAllPhases = newMarkers();
-
-  for (let m of profile.markers.data) {
-    let markerName = profile.stringTable[m[nameCol]];
-    if (markerName.startsWith("BackgroundTasksManager:")) {
-      phases[
-        markerName.split("BackgroundTasksManager:")[1]
-      ] = markersForCurrentPhase;
-      markersForCurrentPhase = newMarkers();
-      continue;
-    }
-
-    if (
-      ![
-        "ChromeUtils.import", // JSMs.
-        "JS XPCOM", // JavaScript XPCOM components.
-        "GetService", // XPCOM services.
-      ].includes(markerName)
-    ) {
-      continue;
-    }
-
-    let markerData = m[dataCol];
-    if (markerName == "ChromeUtils.import") {
-      let module = markerData.name;
-      if (!markersForAllPhases.modules.includes(module)) {
-        markersForAllPhases.modules.push(module);
-        markersForCurrentPhase.modules.push(module);
-      }
-    }
-
-    if (markerName == "JS XPCOM") {
-      // The stack will always contain a label like
-      // `mozJSComponentLoader::LoadModule ...`.  Extract the path from that.
-      let samples = markerData.stack.samples;
-      let stackId = samples.data[0][samples.schema.stack];
-      let stackLines = getStackFromProfile(profile, stackId, rootProfile.libs);
-
-      let component = stackLines
-        .filter(s => s.startsWith("mozJSComponentLoader::LoadModule"))[0]
-        .split(" ", 2)[1];
-
-      // Keep only the file name for components, as the path is an absolute file
-      // URL rather than a resource:// URL like for modules.
-      component = component.replace(/.*\//, "");
-
-      if (!markersForAllPhases.components.includes(component)) {
-        markersForAllPhases.components.push(component);
-        markersForCurrentPhase.components.push(component);
-      }
-    }
-
-    if (markerName == "GetService") {
-      // We get a CID from the marker itself, but not a human-readable contract
-      // ID.  Now, most of the time, the stack will contain a label like
-      // `GetServiceByContractID @...;1`, and we could extract the contract ID
-      // from that.  But there are multiple ways to instantiate services, and
-      // not all of them are annotated in this manner.  Therefore we "go the
-      // other way" and use the component manager's mapping from contract IDs to
-      // CIDs.  This opens up the possibility for that mapping to be different
-      // between `--backgroundtask` and `xpcshell`, but that's not an issue
-      // right at this moment.  It's worth noting that one CID can (and
-      // sometimes does) correspond to more than one contract ID.
-      let cid = markerData.name;
-
-      if (!markersForAllPhases.services.includes(cid)) {
-        markersForAllPhases.services.push(cid);
-        markersForCurrentPhase.services.push(cid);
-      }
-    }
-  }
-
-  // Turn `["1", {name: "2", condition: false}, {name: "3", condition: true}]`
-  // into `new Set(["1", "3"])`.
-  function filterConditions(l) {
-    let set = new Set([]);
-    for (let entry of l) {
-      if (typeof entry == "object") {
-        if ("condition" in entry && !entry.condition) {
-          continue;
-        }
-        entry = entry.name;
-      }
-      set.add(entry);
-    }
-    return set;
-  }
-
-  for (let phaseName in backgroundtaskPhases) {
-    for (let listName in backgroundtaskPhases[phaseName]) {
-      for (let scriptType in backgroundtaskPhases[phaseName][listName]) {
-        backgroundtaskPhases[phaseName][listName][
-          scriptType
-        ] = filterConditions(
-          backgroundtaskPhases[phaseName][listName][scriptType]
-        );
-      }
-
-      // Turn human-readable contract IDs into CIDs.  It's worth noting that one
-      // CID can (and sometimes does) correspond to more than one contract ID.
-      let services = Array.from(
-        backgroundtaskPhases[phaseName][listName].services || new Set([])
-      );
-      services = services
-        .map(contractID => {
-          try {
-            return Cm.contractIDToCID(contractID).toString();
-          } catch (e) {
-            return null;
-          }
-        })
-        .filter(cid => cid);
-      services.sort();
-      backgroundtaskPhases[phaseName][listName].services = new Set(services);
-      info(
-        `backgroundtaskPhases[${phaseName}][${listName}].services = ${JSON.stringify(
-          services.map(c => c.toString())
-        )}`
-      );
-    }
-  }
-
-  // Turn `{CID}` into `{CID} (@contractID)` or `{CID} (one of
-  // @contractID1, ..., @contractIDn)` as appropriate.
-  function renderResource(resource) {
-    const UUID_PATTERN = /^\{[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}\}$/i;
-    if (UUID_PATTERN.test(resource)) {
-      let foundContractIDs = [];
-      for (let contractID of Cm.getContractIDs()) {
-        try {
-          if (resource == Cm.contractIDToCID(contractID).toString()) {
-            foundContractIDs.push(contractID);
-          }
-        } catch (e) {
-          // This can throw for contract IDs that are filtered.  The common
-          // reason is that they're limited to a particular process.
-        }
-      }
-      if (!foundContractIDs.length) {
-        return `${resource} (CID with no human-readable contract IDs)`;
-      } else if (foundContractIDs.length == 1) {
-        return `${resource} (CID with human-readable contract ID ${foundContractIDs[0]})`;
-      }
-      foundContractIDs.sort();
-      return `${resource} (CID with human-readable contract IDs ${JSON.stringify(
-        foundContractIDs
-      )})`;
-    }
-
-    return resource;
-  }
-
-  for (let phase in backgroundtaskPhases) {
-    let loadedList = phases[phase];
-    let allowlist = backgroundtaskPhases[phase].allowlist || null;
-    if (allowlist) {
-      for (let scriptType in allowlist) {
-        loadedList[scriptType] = loadedList[scriptType].filter(c => {
-          if (!allowlist[scriptType].has(c)) {
-            return true;
-          }
-          allowlist[scriptType].delete(c);
-          return false;
-        });
-        Assert.deepEqual(
-          loadedList[scriptType],
-          [],
-          `${phase}: should have no unexpected ${scriptType} loaded`
-        );
-
-        // Present errors in deterministic order.
-        let unexpected = Array.from(loadedList[scriptType]);
-        unexpected.sort();
-        for (let script of unexpected) {
-          // It would be nice to show stacks here, but that can be follow-up.
-          ok(
-            false,
-            `${phase}: unexpected ${scriptType}: ${renderResource(script)}`
-          );
-        }
-        Assert.deepEqual(
-          allowlist[scriptType].size,
-          0,
-          `${phase}: all ${scriptType} allowlist entries should have been used`
-        );
-        let unused = Array.from(allowlist[scriptType]);
-        unused.sort();
-        for (let script of unused) {
-          ok(
-            false,
-            `${phase}: unused ${scriptType} allowlist entry: ${renderResource(
-              script
-            )}`
-          );
-        }
-      }
-    }
-    let denylist = backgroundtaskPhases[phase].denylist || null;
-    if (denylist) {
-      for (let scriptType in denylist) {
-        let resources = denylist[scriptType];
-        resources.sort();
-        for (let resource of resources) {
-          let loaded = loadedList[scriptType].includes(resource);
-          let message = `${phase}: ${renderResource(resource)} is not allowed`;
-          // It would be nice to show stacks here, but that can be follow-up.
-          ok(!loaded, message);
-        }
-      }
-    }
-  }
-});
diff --git a/toolkit/components/backgroundtasks/tests/browser/head.js b/toolkit/components/backgroundtasks/tests/browser/head.js
deleted file mode 100644
index fb9c3fe123a0..000000000000
--- a/toolkit/components/backgroundtasks/tests/browser/head.js
+++ /dev/null
@@ -1,66 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * vim: sw=4 ts=4 sts=4 et
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-async function do_backgroundtask(
-  task,
-  options = { extraArgs: [], extraEnv: {} }
-) {
-  options = Object.assign({}, options);
-  options.extraArgs = options.extraArgs || [];
-  options.extraEnv = options.extraEnv || {};
-
-  let command = Services.dirsvc.get("XREExeF", Ci.nsIFile).path;
-  let args = ["--backgroundtask", task];
-  args.push(...options.extraArgs);
-
-  // Ensure `resource://testing-common` gets mapped.
-  let protocolHandler = Services.io
-    .getProtocolHandler("resource")
-    .QueryInterface(Ci.nsIResProtocolHandler);
-
-  let uri = protocolHandler.getSubstitution("testing-common");
-  Assert.ok(uri, "resource://testing-common is not substituted");
-
-  // The equivalent of _TESTING_MODULES_DIR in xpcshell.
-  options.extraEnv.XPCSHELL_TESTING_MODULES_URI = uri.spec;
-
-  // Now we can actually invoke the process.
-  info(
-    `launching child process ${command} with args: ${args} and extra environment: ${JSON.stringify(
-      options.extraEnv
-    )}`
-  );
-
-  const { Subprocess } = ChromeUtils.import(
-    "resource://gre/modules/Subprocess.jsm"
-  );
-  let proc = await Subprocess.call({
-    command,
-    arguments: args,
-    environment: options.extraEnv,
-    environmentAppend: true,
-    stderr: "stdout",
-  }).then(p => {
-    p.stdin.close();
-    const dumpPipe = async pipe => {
-      let data = await pipe.readString();
-      while (data) {
-        for (let line of data.split(/\r\n|\r|\n/).slice(0, -1)) {
-          dump("> " + line + "\n");
-        }
-        data = await pipe.readString();
-      }
-    };
-    dumpPipe(p.stdout);
-
-    return p;
-  });
-
-  let { exitCode } = await proc.wait();
-  return exitCode;
-}
diff --git a/toolkit/components/backgroundtasks/tests/xpcshell/head.js b/toolkit/components/backgroundtasks/tests/xpcshell/head.js
deleted file mode 100644
index 58105a36145f..000000000000
--- a/toolkit/components/backgroundtasks/tests/xpcshell/head.js
+++ /dev/null
@@ -1,86 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * vim: sw=4 ts=4 sts=4 et
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-const { AppConstants } = ChromeUtils.import(
-  "resource://gre/modules/AppConstants.jsm"
-);
-const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
-const { Subprocess } = ChromeUtils.import(
-  "resource://gre/modules/Subprocess.jsm"
-);
-
-function getFirefoxExecutableFilename() {
-  if (AppConstants.platform === "win") {
-    return AppConstants.MOZ_APP_NAME + ".exe";
-  }
-  return AppConstants.MOZ_APP_NAME;
-}
-
-// Returns a nsIFile to the firefox.exe (really, application) executable file.
-function getFirefoxExecutableFile() {
-  let file = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
-  file = Services.dirsvc.get("GreBinD", Ci.nsIFile);
-
-  file.append(getFirefoxExecutableFilename());
-  return file;
-}
-
-async function do_backgroundtask(
-  task,
-  options = { extraArgs: [], extraEnv: {} }
-) {
-  options = Object.assign({}, options);
-  options.extraArgs = options.extraArgs || [];
-  options.extraEnv = options.extraEnv || {};
-
-  let command = getFirefoxExecutableFile().path;
-  let args = ["--backgroundtask", task];
-  args.push(...options.extraArgs);
-
-  // Ensure `resource://testing-common` gets mapped.
-  let protocolHandler = Services.io
-    .getProtocolHandler("resource")
-    .QueryInterface(Ci.nsIResProtocolHandler);
-
-  let uri = protocolHandler.getSubstitution("testing-common");
-  Assert.ok(uri, "resource://testing-common is not substituted");
-
-  // The equivalent of _TESTING_MODULES_DIR in xpcshell.
-  options.extraEnv.XPCSHELL_TESTING_MODULES_URI = uri.spec;
-
-  // Now we can actually invoke the process.
-  info(
-    `launching child process ${command} with args: ${args} and extra environment: ${JSON.stringify(
-      options.extraEnv
-    )}`
-  );
-  let proc = await Subprocess.call({
-    command,
-    arguments: args,
-    environment: options.extraEnv,
-    environmentAppend: true,
-    stderr: "stdout",
-  }).then(p => {
-    p.stdin.close();
-    const dumpPipe = async pipe => {
-      let data = await pipe.readString();
-      while (data) {
-        for (let line of data.split(/\r\n|\r|\n/).slice(0, -1)) {
-          dump("> " + line + "\n");
-        }
-        data = await pipe.readString();
-      }
-    };
-    dumpPipe(p.stdout);
-
-    return p;
-  });
-
-  let { exitCode } = await proc.wait();
-  return exitCode;
-}
diff --git a/toolkit/components/backgroundtasks/tests/xpcshell/test_backgroundtask_exitcodes.js b/toolkit/components/backgroundtasks/tests/xpcshell/test_backgroundtask_exitcodes.js
deleted file mode 100644
index b9edf97f7d8f..000000000000
--- a/toolkit/components/backgroundtasks/tests/xpcshell/test_backgroundtask_exitcodes.js
+++ /dev/null
@@ -1,25 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * vim: sw=4 ts=4 sts=4 et
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-add_task(async function test_success() {
-  let exitCode = await do_backgroundtask("success");
-  Assert.equal(0, exitCode);
-});
-
-add_task(async function test_failure() {
-  let exitCode = await do_backgroundtask("failure");
-  Assert.equal(1, exitCode);
-});
-
-add_task(async function test_exception() {
-  let exitCode = await do_backgroundtask("exception");
-  Assert.equal(3, exitCode);
-});
-
-add_task(async function test_not_found() {
-  let exitCode = await do_backgroundtask("not_found");
-  Assert.equal(2, exitCode);
-});
diff --git a/toolkit/components/backgroundtasks/tests/xpcshell/test_backgroundtask_policies.js b/toolkit/components/backgroundtasks/tests/xpcshell/test_backgroundtask_policies.js
deleted file mode 100644
index bf4f6199e347..000000000000
--- a/toolkit/components/backgroundtasks/tests/xpcshell/test_backgroundtask_policies.js
+++ /dev/null
@@ -1,45 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * vim: sw=4 ts=4 sts=4 et
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-// In order to use the policy engine inside the xpcshell harness, we need to set
-// up a dummy app info.  In the backgroundtask itself, the application under
-// test will configure real app info.  This opens a possibility for some
-// incompatibility, but there doesn't appear to be such an issue at this time.
-const { updateAppInfo } = ChromeUtils.import(
-  "resource://testing-common/AppInfo.jsm"
-);
-updateAppInfo({
-  name: "XPCShell",
-  ID: "xpcshell@tests.mozilla.org",
-  version: "48",
-  platformVersion: "48",
-});
-
-const { EnterprisePolicyTesting } = ChromeUtils.import(
-  "resource://testing-common/EnterprisePolicyTesting.jsm"
-);
-
-// This initializes the policy engine for xpcshell tests
-let policies = Cc["@mozilla.org/enterprisepolicies;1"].getService(
-  Ci.nsIObserver
-);
-policies.observe(null, "policies-startup", null);
-
-add_task(async function test_backgroundtask_policies() {
-  let url = "https://www.example.com/";
-  await EnterprisePolicyTesting.setupPolicyEngineWithJson({
-    policies: {
-      AppUpdateURL: url,
-    },
-  });
-
-  let filePath = Services.prefs.getStringPref("browser.policies.alternatePath");
-
-  let exitCode = await do_backgroundtask("policies", {
-    extraArgs: [filePath, url],
-  });
-  Assert.equal(0, exitCode);
-});
diff --git a/toolkit/components/backgroundtasks/tests/xpcshell/test_backgroundtask_specific_pref.js b/toolkit/components/backgroundtasks/tests/xpcshell/test_backgroundtask_specific_pref.js
deleted file mode 100644
index 50f85b9becb7..000000000000
--- a/toolkit/components/backgroundtasks/tests/xpcshell/test_backgroundtask_specific_pref.js
+++ /dev/null
@@ -1,20 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
- * vim: sw=4 ts=4 sts=4 et
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-add_task(async function test_backgroundtask_specific_pref() {
-  // First, verify this pref isn't set in Gecko itself.
-  Assert.equal(
-    -1,
-    Services.prefs.getIntPref("test.backgroundtask_specific_pref.exitCode", -1)
-  );
-
-  // Second, verify that this pref is set in background tasks.
-  // xpcshell tests locally test unpackaged builds.
-  let exitCode = await do_backgroundtask("backgroundtask_specific_pref", {
-    extraArgs: ["test.backgroundtask_specific_pref.exitCode"],
-  });
-  Assert.equal(79, exitCode);
-});
diff --git a/toolkit/components/backgroundtasks/tests/xpcshell/test_manifest_with_backgroundtask.js b/toolkit/components/backgroundtasks/tests/xpcshell/test_manifest_with_backgroundtask.js
index f713fe5e782b..5442d1961180 100644
--- a/toolkit/components/backgroundtasks/tests/xpcshell/test_manifest_with_backgroundtask.js
+++ b/toolkit/components/backgroundtasks/tests/xpcshell/test_manifest_with_backgroundtask.js
@@ -4,6 +4,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
+
 add_task(async function test_manifest_with_backgroundtask() {
   let bts = Cc["@mozilla.org/backgroundtasks;1"].getService(
     Ci.nsIBackgroundTasks
diff --git a/toolkit/components/backgroundtasks/tests/xpcshell/test_manifest_without_backgroundtask.js b/toolkit/components/backgroundtasks/tests/xpcshell/test_manifest_without_backgroundtask.js
index 422d9a49ff6a..e3d7936feecf 100644
--- a/toolkit/components/backgroundtasks/tests/xpcshell/test_manifest_without_backgroundtask.js
+++ b/toolkit/components/backgroundtasks/tests/xpcshell/test_manifest_without_backgroundtask.js
@@ -4,6 +4,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
+
 add_task(async function test_without_backgroundtask() {
   let bts = Cc["@mozilla.org/backgroundtasks;1"].getService(
     Ci.nsIBackgroundTasks
diff --git a/toolkit/components/backgroundtasks/tests/xpcshell/xpcshell.ini b/toolkit/components/backgroundtasks/tests/xpcshell/xpcshell.ini
index c1b42a2ff56c..b39f03003eee 100644
--- a/toolkit/components/backgroundtasks/tests/xpcshell/xpcshell.ini
+++ b/toolkit/components/backgroundtasks/tests/xpcshell/xpcshell.ini
@@ -3,14 +3,9 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 [DEFAULT]
-firefox-appdir = browser
 skip-if = toolkit == 'android'
-head = head.js
 support-files =
   CatBackgroundTaskRegistrationComponents.manifest
 
-[test_backgroundtask_exitcodes.js]
-[test_backgroundtask_policies.js]
-[test_backgroundtask_specific_pref.js]
 [test_manifest_with_backgroundtask.js]
 [test_manifest_without_backgroundtask.js]
diff --git a/toolkit/crashreporter/test/unit/head_crashreporter.js b/toolkit/crashreporter/test/unit/head_crashreporter.js
index d4b9669d2b29..a9a99c171a62 100644
--- a/toolkit/crashreporter/test/unit/head_crashreporter.js
+++ b/toolkit/crashreporter/test/unit/head_crashreporter.js
@@ -261,89 +261,6 @@ async function do_triggered_content_crash(trigger, callback) {
   }
 }
 
-/*
- * Run the `crash` backgroundtask subprocess, crashing it in the
- * specified manner.
- *
- * @param crashType Integer `CrashTestUtils.CRASH_...` code.
- * @param crashExtras Dictionary of key-value pairs to include in
- *                    minidump extras.
- *
- * @param callback
- *        A JavaScript function to be called after the subprocess
- *        crashes. It will be passed (minidump, extra, extrafile), where
- *         - minidump is an nsIFile of the minidump file produced,
- *         - extra is an object containing the key,value pairs from
- *           the .extra file.
- *         - extrafile is an nsIFile of the extra file
- *
- * @param canReturnZero
- *       If true, the subprocess may return with a zero exit code.
- *       Certain types of crashes may not cause the process to
- *       exit with an error.
- *
- */
-async function do_backgroundtask_crash(
-  crashType,
-  crashExtras,
-  callback,
-  canReturnZero
-) {
-  Assert.ok(AppConstants.MOZ_BACKGROUNDTASKS);
-
-  // Get full path to application (not xpcshell)
-  let bin = Services.dirsvc.get("GreBinD", Ci.nsIFile);
-  if (AppConstants.platform === "win") {
-    bin.append(AppConstants.MOZ_APP_NAME + ".exe");
-  } else {
-    bin.append(AppConstants.MOZ_APP_NAME);
-  }
-
-  // run `application --backgroundtask crash ...`.
-  let process = Cc["@mozilla.org/process/util;1"].createInstance(Ci.nsIProcess);
-  process.init(bin);
-
-  let args = ["--backgroundtask", "crash"];
-  args.push(crashType.toString());
-
-  // Sorted to be deterministic.
-  let sorted = Object.entries(crashExtras).sort((a, b) => a[0] < b[0]);
-  for (let [key, value] of sorted) {
-    args.push(key);
-    args.push(value);
-  }
-
-  let env = Cc["@mozilla.org/process/environment;1"].getService(
-    Ci.nsIEnvironment
-  );
-
-  let crashD = do_get_tempdir();
-  crashD.append("crash-events");
-  if (!crashD.exists()) {
-    crashD.create(crashD.DIRECTORY_TYPE, 0o700);
-  }
-
-  env.set("CRASHES_EVENTS_DIR", crashD.path);
-  // Used to map resource://testing-common.
-  env.set("XPCSHELL_TESTING_MODULES_DIR", _TESTING_MODULES_DIR);
-
-  try {
-    process.run(true, args, args.length);
-  } catch (ex) {
-    // on Windows we exit with a -1 status when crashing.
-  } finally {
-    env.set("CRASHES_EVENTS_DIR", "");
-    env.set("XPCSHELL_TESTING_MODULES_DIR", "");
-  }
-
-  if (!canReturnZero) {
-    // should exit with an error (should have crashed)
-    Assert.notEqual(process.exitValue, 0);
-  }
-
-  await handleMinidump(callback);
-}
-
 // Import binary APIs via js-ctypes.
 var { CrashTestUtils } = ChromeUtils.import(
   "resource://test/CrashTestUtils.jsm"
diff --git a/toolkit/crashreporter/test/unit/test_crash_backgroundtask_moz_crash.js b/toolkit/crashreporter/test/unit/test_crash_backgroundtask_moz_crash.js
deleted file mode 100644
index 1eb0e0a68869..000000000000
--- a/toolkit/crashreporter/test/unit/test_crash_backgroundtask_moz_crash.js
+++ /dev/null
@@ -1,22 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
- * http://creativecommons.org/publicdomain/zero/1.0/ */
-
-add_task(async function run_test() {
-  if (!AppConstants.MOZ_BACKGROUNDTASKS) {
-    return;
-  }
-
-  // Try crashing background task with a runtime abort
-  await do_backgroundtask_crash(
-    CrashTestUtils.CRASH_MOZ_CRASH,
-    { TestKey: "TestValue" },
-    function(mdump, extra) {
-      Assert.equal(extra.TestKey, "TestValue");
-      Assert.equal(false, "OOMAllocationSize" in extra);
-      Assert.equal(false, "JSOutOfMemory" in extra);
-      Assert.equal(false, "JSLargeAllocationFailure" in extra);
-    },
-    // process will exit with a zero exit status
-    true
-  );
-});
diff --git a/toolkit/crashreporter/test/unit/xpcshell.ini b/toolkit/crashreporter/test/unit/xpcshell.ini
index 127c97b73819..65882e7447cd 100644
--- a/toolkit/crashreporter/test/unit/xpcshell.ini
+++ b/toolkit/crashreporter/test/unit/xpcshell.ini
@@ -39,8 +39,6 @@ skip-if = (os != 'win' && os != 'linux') || (os=='linux' && bits==32)
 [test_event_files.js]
 [test_crash_terminator.js]
 
-[test_crash_backgroundtask_moz_crash.js]
-
 [test_crash_heap_corruption.js]
 skip-if = os != 'win'
 
diff --git a/toolkit/xre/moz.build b/toolkit/xre/moz.build
index cf5f7ac50093..edaabb958d98 100644
--- a/toolkit/xre/moz.build
+++ b/toolkit/xre/moz.build
@@ -285,6 +285,3 @@ if CONFIG["MOZ_IPDL_TESTS"]:
 
 if CONFIG["ENABLE_TESTS"]:
     DIRS += ["test/gtest"]
-
-if CONFIG["MOZ_BACKGROUNDTASKS"]:
-    DEFINES["MOZ_BACKGROUNDTASKS"] = True
diff --git a/toolkit/xre/nsAppRunner.cpp b/toolkit/xre/nsAppRunner.cpp
index 22bc9c076198..e23c1a29eee3 100644
--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -248,12 +248,6 @@
 #  include "nsIPK11Token.h"
 #endif
 
-#ifdef MOZ_BACKGROUNDTASKS
-#  include "mozilla/BackgroundTasks.h"
-#  include "nsIPowerManagerService.h"
-#  include "nsIStringBundle.h"
-#endif
-
 extern uint32_t gRestartMode;
 extern void InstallSignalHandlers(const char* ProgramName);
 
@@ -2281,15 +2275,6 @@ class ReturnAbortOnError {
 }  // namespace
 
 static nsresult ProfileMissingDialog(nsINativeAppSupport* aNative) {
-#ifdef MOZ_BACKGROUNDTASKS
-  if (BackgroundTasks::IsBackgroundTaskMode()) {
-    // We should never get to this point in background task mode.
-    Output(false,
-           "Could not determine any profile running in backgroundtask mode!\n");
-    return NS_ERROR_ABORT;
-  }
-#endif
-
   nsresult rv;
 
   ScopedXPCOMStartup xpcom;
@@ -3476,26 +3461,10 @@ int XREMain::XRE_mainInit(bool* aExitFlag) {
   DisableAppNap();
 #endif
 
-#ifdef MOZ_BACKGROUNDTASKS
-  Maybe<nsCString> backgroundTask = Nothing();
-  const char* backgroundTaskName = nullptr;
-  if (ARG_FOUND == CheckArg("backgroundtask", &backgroundTaskName)) {
-    backgroundTask = Some(backgroundTaskName);
-  }
-  BackgroundTasks::Init(backgroundTask);
-
-  if (BackgroundTasks::IsBackgroundTaskMode()) {
-    printf_stderr("*** You are running in background task mode. ***\n");
-  }
-#endif
-
 #ifndef ANDROID
   if (PR_GetEnv("MOZ_RUN_GTEST")
 #  ifdef FUZZING
       || PR_GetEnv("FUZZER")
-#  endif
-#  ifdef MOZ_BACKGROUNDTASKS
-      || BackgroundTasks::IsBackgroundTaskMode()
 #  endif
   ) {
     // Enable headless mode and assert that it worked, since gfxPlatform
@@ -3843,11 +3812,6 @@ int XREMain::XRE_mainInit(bool* aExitFlag) {
   if (!safeModeRequested) {
     return 1;
   }
-#ifdef MOZ_BACKGROUNDTASKS
-  if (BackgroundTasks::IsBackgroundTaskMode()) {
-    safeModeRequested = Some(false);
-  }
-#endif
 
   gSafeMode = safeModeRequested.value();
 
@@ -4433,19 +4397,6 @@ int XREMain::XRE_mainStartup(bool* aExitFlag) {
     return 1;
   }
 
-#ifdef MOZ_BACKGROUNDTASKS
-  if (BackgroundTasks::IsBackgroundTaskMode()) {
-    nsCOMPtr<nsIFile> file;
-    nsresult rv = BackgroundTasks::GetOrCreateTemporaryProfileDirectory(
-        getter_AddRefs(file));
-    if (NS_WARN_IF(NS_FAILED(rv))) {
-      return 1;
-    }
-
-    SaveFileToEnv("XRE_PROFILE_PATH", file);
-  }
-#endif
-
   bool wasDefaultSelection;
   nsCOMPtr<nsIToolkitProfile> profile;
   rv = SelectProfile(mProfileSvc, mNativeApp, getter_AddRefs(mProfD),
@@ -4783,9 +4734,6 @@ nsresult XREMain::XRE_mainRun() {
   // We need the appStartup pointer to span multiple scopes, so we declare
   // it here.
   nsCOMPtr<nsIAppStartup> appStartup;
-  // Ditto with the command line.
-  nsCOMPtr<nsICommandLineRunner> cmdLine;
-
   {
 #ifdef XP_MACOSX
     // In this scope, create an autorelease pool that will leave scope with
@@ -5011,6 +4959,8 @@ nsresult XREMain::XRE_mainRun() {
 
     appStartup->GetShuttingDown(&mShuttingDown);
 
+    nsCOMPtr<nsICommandLineRunner> cmdLine;
+
     nsCOMPtr<nsIFile> workingDir;
     rv = NS_GetSpecialDirectory(NS_OS_CURRENT_WORKING_DIR,
                                 getter_AddRefs(workingDir));
@@ -5067,13 +5017,6 @@ nsresult XREMain::XRE_mainRun() {
           Preferences::GetBool("toolkit.lazyHiddenWindow", false);
 #endif
 
-#ifdef MOZ_BACKGROUNDTASKS
-      if (BackgroundTasks::IsBackgroundTaskMode()) {
-        // Background tasks aren't going to load a chrome XUL document.
-        lazyHiddenWindow = true;
-      }
-#endif
-
       if (!lazyHiddenWindow) {
         rv = appStartup->CreateHiddenWindow();
         NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
@@ -5089,26 +5032,18 @@ nsresult XREMain::XRE_mainRun() {
       SetupLauncherProcessPref();
 #  endif  // defined(MOZ_LAUNCHER_PROCESS)
 #  if defined(MOZ_DEFAULT_BROWSER_AGENT)
-#    if defined(MOZ_BACKGROUNDTASKS)
-      // The backgroundtask profile is not a browsing profile, let alone the new
-      // default profile, so don't mirror its properties into the registry.
-      if (!BackgroundTasks::IsBackgroundTaskMode())
-#    endif  // defined(MOZ_BACKGROUNDTASKS)
-      {
-        Preferences::RegisterCallbackAndCall(
-            &OnDefaultAgentTelemetryPrefChanged,
-            kPrefHealthReportUploadEnabled);
-        Preferences::RegisterCallbackAndCall(
-            &OnDefaultAgentTelemetryPrefChanged, kPrefDefaultAgentEnabled);
+      Preferences::RegisterCallbackAndCall(&OnDefaultAgentTelemetryPrefChanged,
+                                           kPrefHealthReportUploadEnabled);
+      Preferences::RegisterCallbackAndCall(&OnDefaultAgentTelemetryPrefChanged,
+                                           kPrefDefaultAgentEnabled);
 
-        Preferences::RegisterCallbackAndCall(
-            &OnDefaultAgentRemoteSettingsPrefChanged,
-            kPrefServicesSettingsServer);
-        Preferences::RegisterCallbackAndCall(
-            &OnDefaultAgentRemoteSettingsPrefChanged,
-            kPrefSecurityContentSignatureRootHash);
-        SetDefaultAgentLastRunTime();
-      }
+      Preferences::RegisterCallbackAndCall(
+          &OnDefaultAgentRemoteSettingsPrefChanged,
+          kPrefServicesSettingsServer);
+      Preferences::RegisterCallbackAndCall(
+          &OnDefaultAgentRemoteSettingsPrefChanged,
+          kPrefSecurityContentSignatureRootHash);
+      SetDefaultAgentLastRunTime();
 #  endif  // defined(MOZ_DEFAULT_BROWSER_AGENT)
 #endif
 
@@ -5220,30 +5155,6 @@ nsresult XREMain::XRE_mainRun() {
     mProfileSvc->CompleteStartup();
   }
 
-#ifdef MOZ_BACKGROUNDTASKS
-  if (BackgroundTasks::IsBackgroundTaskMode()) {
-    // In background task mode, we don't fire various delayed initialization
-    // notifications, which in the regular browser is how startup crash tracking
-    // is marked as finished.  Here, getting this far means we don't have a
-    // startup crash.
-    rv = appStartup->TrackStartupCrashEnd();
-    NS_ENSURE_SUCCESS(rv, rv);
-
-    // We never open a window, but don't want to exit immediately.
-    rv = appStartup->EnterLastWindowClosingSurvivalArea();
-    NS_ENSURE_SUCCESS(rv, rv);
-
-    // Avoid some small differences in initialization order across platforms.
-    nsCOMPtr<nsIPowerManagerService> powerManagerService =
-        do_GetService(POWERMANAGERSERVICE_CONTRACTID);
-    nsCOMPtr<nsIStringBundleService> stringBundleService =
-        do_GetService(NS_STRINGBUNDLE_CONTRACTID);
-
-    rv = BackgroundTasks::RunBackgroundTask(cmdLine);
-    NS_ENSURE_SUCCESS(rv, rv);
-  }
-#endif
-
   {
     rv = appStartup->Run();
     if (NS_FAILED(rv)) {
@@ -5465,10 +5376,6 @@ int XREMain::XRE_main(int argc, char* argv[], const BootstrapConfig& aConfig) {
   mProfileLock->Unlock();
   gProfileLock = nullptr;
 
-#ifdef MOZ_BACKGROUNDTASKS
-  BackgroundTasks::Shutdown();
-#endif
-
   gLastAppVersion.Truncate();
   gLastAppBuildID.Truncate();
 
diff --git a/toolkit/xre/nsXREDirProvider.cpp b/toolkit/xre/nsXREDirProvider.cpp
index c9ba0f294cb2..d9bcdb1f4e26 100644
--- a/toolkit/xre/nsXREDirProvider.cpp
+++ b/toolkit/xre/nsXREDirProvider.cpp
@@ -39,9 +39,6 @@
 #include "mozilla/dom/ScriptSettings.h"
 
 #include "mozilla/AutoRestore.h"
-#ifdef MOZ_BACKGROUNDTASKS
-#  include "mozilla/BackgroundTasks.h"
-#endif
 #include "mozilla/Components.h"
 #include "mozilla/Services.h"
 #include "mozilla/Omnijar.h"
@@ -853,10 +850,6 @@ static nsresult DeleteDirIfExists(nsIFile* dir) {
 
 static const char* const kAppendPrefDir[] = {"defaults", "preferences",
                                              nullptr};
-#ifdef MOZ_BACKGROUNDTASKS
-static const char* const kAppendBackgroundTasksPrefDir[] = {
-    "defaults", "backgroundtasks", nullptr};
-#endif
 
 nsresult nsXREDirProvider::GetFilesInternal(const char* aProperty,
                                             nsISimpleEnumerator** aResult) {
@@ -867,12 +860,6 @@ nsresult nsXREDirProvider::GetFilesInternal(const char* aProperty,
     nsCOMArray<nsIFile> directories;
 
     LoadDirIntoArray(mXULAppDir, kAppendPrefDir, directories);
-#ifdef MOZ_BACKGROUNDTASKS
-    if (mozilla::BackgroundTasks::IsBackgroundTaskMode()) {
-      LoadDirIntoArray(mGREDir, kAppendBackgroundTasksPrefDir, directories);
-      LoadDirIntoArray(mXULAppDir, kAppendBackgroundTasksPrefDir, directories);
-    }
-#endif
 
     rv = NS_NewArrayEnumerator(aResult, directories, NS_GET_IID(nsIFile));
   } else if (!strcmp(aProperty, NS_APP_CHROME_DIR_LIST)) {
@@ -979,21 +966,13 @@ nsXREDirProvider::DoStartup() {
     mozilla::SandboxBroker::GeckoDependentInitialize();
 #endif
 
-    bool initExtensionManager =
-#ifdef MOZ_BACKGROUNDTASKS
-        !mozilla::BackgroundTasks::IsBackgroundTaskMode();
-#else
-        true;
-#endif
-    if (initExtensionManager) {
-      // Init the Extension Manager
-      nsCOMPtr<nsIObserver> em =
-          do_GetService("@mozilla.org/addons/integration;1");
-      if (em) {
-        em->Observe(nullptr, "addons-startup", nullptr);
-      } else {
-        NS_WARNING("Failed to create Addons Manager.");
-      }
+    // Init the Extension Manager
+    nsCOMPtr<nsIObserver> em =
+        do_GetService("@mozilla.org/addons/integration;1");
+    if (em) {
+      em->Observe(nullptr, "addons-startup", nullptr);
+    } else {
+      NS_WARNING("Failed to create Addons Manager.");
     }
 
     obsSvc->NotifyObservers(nullptr, "profile-after-change", kStartup);