Bug 1897060 - Gather process lifetime telemetry r=ipc-reviewers,mccr8

Differential Revision: https://phabricator.services.mozilla.com/D210751

dom/ipc/ContentParent.cpp

@@ -2039,6 +2039,14 @@ void ContentParent::ActorDestroy(ActorDestroyReason why) {
   MOZ_FUZZING_IPC_DROP_PEER("ContentParent::ActorDestroy");
 #endif
 
+  // Gather process lifetime telemetry.
+  if (StringBeginsWith(mRemoteType, WEB_REMOTE_TYPE) ||
+      mRemoteType == FILE_REMOTE_TYPE || mRemoteType == EXTENSION_REMOTE_TYPE) {
+    TimeDuration runtime = TimeStamp::Now() - mActivateTS;
+    Telemetry::Accumulate(Telemetry::PROCESS_LIFETIME,
+                          uint64_t(runtime.ToSeconds()));
+  }
+
   if (mSendShutdownTimer) {
     mSendShutdownTimer->Cancel();
     mSendShutdownTimer = nullptr;

toolkit/components/telemetry/Histograms.json

@@ -1790,6 +1790,19 @@
     "description": "Number of PHC slots allocated-then-freed",
     "releaseChannelCollection": "opt-out"
   },
+  "PROCESS_LIFETIME": {
+    "record_in_processes": ["main"],
+    "products": ["firefox"],
+    "alert_emails": ["pbone@mozilla.com"],
+    "bug_numbers": [1897060],
+    "expires_in_version": "135",
+    "kind": "exponential",
+    "low": 15,
+    "high": 86400,
+    "n_buckets": 24,
+    "description": "Average lifetime of a content process in seconds",
+    "releaseChannelCollection": "opt-out"
+  },
 
   "FONTLIST_INITOTHERFAMILYNAMES": {
     "record_in_processes": ["main", "content"],