Bug 1290780. Part 1 - Assert IsShutdown() is false in MediaDecoder::UpdateLogicalPosition(). r=kaku

1. Callbacks from the watch manager are disconnected in Shutdown().
2. It is called from MediaOmxCommonDecoder::NotifyOffloadPlayerPositionChanged() which will not happen after Shutdown().
3. It is called from MediaOmxCommonDecoder::ResumeStateMachine() which returns early when IsShutdown() is true.

MozReview-Commit-ID: COmPFaQzNTq

--HG--
extra : rebase_source : ac88698c66f4586b00fe62ad4dcdbb1cb4ce8542

dom/media/MediaDecoder.h

@@ -416,6 +416,7 @@ private:
   void UpdateLogicalPosition()
   {
     MOZ_ASSERT(NS_IsMainThread());
+    MOZ_ASSERT(!IsShutdown());
     // Per spec, offical position remains stable during pause and seek.
     if (mPlayState == PLAY_STATE_PAUSED || IsSeeking()) {
       return;