Backed out changeset 30839ee209e8 (bug 901097) for mochitest failures on Android and Mulet. r=backout

xpcom/threads/TimerThread.cpp

@@ -127,23 +127,10 @@ public:
 
 } // namespace
 
-// This is a nsICancelableRunnable because we can dispatch it to Workers and
-// those can be shut down at any time, and in these cases, Cancel() is called
-// instead of Run().
-class nsTimerEvent : public nsCancelableRunnable
+class nsTimerEvent : public nsRunnable
 {
 public:
-  NS_IMETHOD Run() override;
-
-  NS_IMETHOD Cancel() override
-  {
-    // Since nsTimerImpl is not thread-safe, we should release |mTimer|
-    // here in the target thread to avoid race condition. Otherwise,
-    // ~nsTimerEvent() which calls nsTimerImpl::Release() could run in the
-    // timer thread and result in race condition.
-    mTimer = nullptr;
-    return NS_OK;
-  }
+  NS_IMETHOD Run();
 
   nsTimerEvent()
     : mTimer()
@@ -266,8 +253,6 @@ nsTimerEvent::DeleteAllocatorIfNeeded()
 NS_IMETHODIMP
 nsTimerEvent::Run()
 {
-  MOZ_ASSERT(mTimer);
-
   if (mGeneration != mTimer->GetGeneration()) {
     return NS_OK;
   }
@@ -280,10 +265,13 @@ nsTimerEvent::Run()
   }
 
   mTimer->Fire();
+  // Since nsTimerImpl is not thread-safe, we should release |mTimer|
+  // here in the target thread to avoid race condition. Otherwise,
+  // ~nsTimerEvent() which calls nsTimerImpl::Release() could run in the
+  // timer thread and result in race condition.
+  mTimer = nullptr;
 
-  // We call Cancel() to correctly release mTimer.
-  // Read more in the Cancel() implementation.
-  return Cancel();
+  return NS_OK;
 }
 
 nsresult