Bug 1885607 - P2: Add ARIAElementReflection pref. r=webidl,smaug

Enable only on nightly for now.

Depends on D204807

Differential Revision: https://phabricator.services.mozilla.com/D204808

dom/webidl/ARIAMixin.webidl

@@ -11,7 +11,7 @@
  */
 
 interface mixin ARIAMixin {
-  [CEReactions]
+  [Pref="accessibility.ARIAElementReflection.enabled", CEReactions]
   attribute Element? ariaActiveDescendantElement;
 
   [CEReactions, SetterThrows]

modules/libpref/init/StaticPrefList.yaml

@@ -220,6 +220,11 @@
   value: false
   mirror: always
 
+- name: accessibility.ARIAElementReflection.enabled
+  type: bool
+  value: @IS_NIGHTLY_BUILD@
+  mirror: always
+
 # Whether form controls and images should be focusable with mouse, in content
 # documents.
 #

testing/web-platform/meta/html/dom/aria-element-reflection-disconnected.html.ini

@@ -1,4 +1,5 @@
 [aria-element-reflection-disconnected.html]
+  prefs: [accessibility.ARIAElementReflection.enabled:true]
   [Element references should stay valid when content is disconnected (element array)]
     expected: FAIL
 

testing/web-platform/meta/html/dom/aria-element-reflection.html.ini

@@ -1,4 +1,5 @@
 [aria-element-reflection.html]
+  prefs: [accessibility.ARIAElementReflection.enabled:true]
   [aria-errormessage]
     expected: FAIL
 

testing/web-platform/meta/wai-aria/idlharness.window.js.ini

@@ -1,4 +1,5 @@
 [idlharness.window.html]
+  prefs: [accessibility.ARIAElementReflection.enabled:true]
   [Element interface: attribute ariaControlsElements]
     expected: FAIL