Bug 1320346 - dump |rv| when AddBlocker() fails to get more debugging info. r=cpearce

MozReview-Commit-ID: LA3uPvdKCU5

--HG--
extra : rebase_source : c75effe6260dfc0318a1c18edd77ebdda68b5b83

dom/media/MediaShutdownManager.cpp

@@ -74,7 +74,16 @@ MediaShutdownManager::EnsureCorrectShutdownObserverState()
       nsresult rv = GetShutdownBarrier()->AddBlocker(
         this, NS_LITERAL_STRING(__FILE__), __LINE__,
         NS_LITERAL_STRING("MediaShutdownManager shutdown"));
-      MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
+      if (NS_FAILED(rv)) {
+        // Leak the buffer on the heap to make sure that it lives long enough,
+        // as MOZ_CRASH_ANNOTATE expects the pointer passed to it to live to
+        // the end of the program.
+        const size_t CAPACITY = 256;
+        auto buf = new char[CAPACITY];
+        snprintf(buf, CAPACITY, "Failed to add shutdown blocker! rv=%x", rv);
+        MOZ_CRASH_ANNOTATE(buf);
+        MOZ_REALLY_CRASH();
+      }
     } else {
       GetShutdownBarrier()->RemoveBlocker(this);
       // Clear our singleton reference. This will probably delete
@@ -89,7 +98,7 @@ void
 MediaShutdownManager::Register(MediaDecoder* aDecoder)
 {
   MOZ_ASSERT(NS_IsMainThread());
-  MOZ_DIAGNOSTIC_ASSERT(!mIsDoingXPCOMShutDown);
+  MOZ_RELEASE_ASSERT(!mIsDoingXPCOMShutDown);
   // Don't call Register() after you've Unregistered() all the decoders,
   // that's not going to work.
   MOZ_ASSERT(!mDecoders.Contains(aDecoder));