Bug 717498 - Clear nsThread::mEventObservers at thread shutdown. r=bsmedberg

xpcom/threads/nsThread.cpp

@@ -506,6 +506,11 @@ nsThread::Shutdown()
   PR_JoinThread(mThread);
   mThread = nsnull;
 
+  // We hold strong references to our event observers, and once the thread is
+  // shut down the observers can't easily unregister themselves. Do it here
+  // to avoid leaking.
+  ClearObservers();
+
 #ifdef DEBUG
   {
     MutexAutoLock lock(mLock);

xpcom/threads/nsThread.h

@@ -77,6 +77,9 @@ public:
   // nsIThreadManager::NewThread.
   bool ShutdownRequired() { return mShutdownRequired; }
 
+  // Clear the observer list.
+  void ClearObservers() { mEventObservers.Clear(); }
+
   // The global thread observer
   static nsIThreadObserver* sGlobalObserver;
 

xpcom/threads/nsThreadManager.cpp

@@ -176,6 +176,7 @@ nsThreadManager::Shutdown()
   // main thread is special we do it manually here after we're sure all events
   // have been processed.
   mMainThread->SetObserver(nsnull);
+  mMainThread->ClearObservers();
 
   // Release main thread object.
   mMainThread = nsnull;