Bug 1708580: When the "quit-application" event fires in GeckoView, annotate the GeckoThread.State and force crash on nightly and early beta; r=agi

AFAICT, all roads lead though [`nsAppStartup::Quit`](https://searchfox.org/mozilla-central/rev/0fec57c05d3996cc00c55a66f20dd5793a9bfb5d/toolkit/components/startup/nsAppStartup.cpp#448),
which is responsible for firing the `"quit-application"` observer notification
and then posting the `nsAppExitEvent` that causes the `nsAppShell` to break out
of its event loop and proceed with shutdown.

If we trigger a native crash in the observer, we should be able to capture a
symbolicated stack of whatever called `Quit`. We might as well force-crash
anyway, since AC is going to throw an exception regardless...

Before we crash, we annotate the current `GeckoThread` state to enable us to
find out whether we were fully initialized at the time of the shutdown.

Differential Revision: https://phabricator.services.mozilla.com/D122256

mobile/android/geckoview/src/main/java/org/mozilla/gecko/GeckoThread.java

@@ -587,6 +587,11 @@ public class GeckoThread extends Thread {
         return isStateAtLeast(minState) && isStateAtMost(maxState);
     }
 
+    @WrapForJNI(calledFrom = "gecko")
+    private static int getStateOrdinal() {
+        return ((State)sNativeQueue.getState()).ordinal();
+    }
+
     @WrapForJNI(calledFrom = "gecko")
     private static void setState(final State newState) {
         checkAndSetState(null, newState);

toolkit/crashreporter/CrashAnnotations.yaml

@@ -298,6 +298,11 @@ ExperimentalFeatures:
   type: string
   ping: true
 
+GeckoViewThreadState:
+  description: >
+    The zero-based ordinal of the GeckoThread.State at the time of the crash.
+  type: integer
+
 GetHGlobalFromStreamFailure:
   description: >
     Error returned when invoking GetHGlobalFromStreamFailure() during the

widget/android/nsAppShell.cpp

@@ -541,6 +541,17 @@ nsAppShell::Observe(nsISupports* aSubject, const char* aTopic,
     }
   } else if (!strcmp(aTopic, "quit-application")) {
     if (jni::IsAvailable()) {
+#if defined(EARLY_BETA_OR_EARLIER)
+      const int curGeckoThreadState = java::GeckoThread::GetStateOrdinal();
+      CrashReporter::AnnotateCrashReport(
+          CrashReporter::Annotation::GeckoViewThreadState, curGeckoThreadState);
+
+      const char* isInAutomation = PR_GetEnv("MOZ_IN_AUTOMATION");
+      if (!isInAutomation || !(*isInAutomation)) {
+        MOZ_CRASH("Something triggered the \"quit-application\" notification!");
+      }
+#endif  // defined(EARLY_BETA_OR_EARLIER)
+
       const bool restarting = aData && u"restart"_ns.Equals(aData);
       java::GeckoThread::SetState(restarting
                                       ? java::GeckoThread::State::RESTARTING()