Avoid unsafe heap access from audio thread.

third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h

Index: third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h
diff --git a/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h b/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h
index 13db3f7c07f6e5eb2acee3eac9a31154841c9a8f..493a6d092a04edfe053586f415bfd6c021dad567 100644
--- a/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h
+++ b/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h
@@ -453,7 +453,9 @@ class MODULES_EXPORT BaseAudioContext
   // it creates these Promises.
   // Handle Promises for resume() and suspend()
   void ResolvePromisesForResume();
-  void ResolvePromisesForResumeOnMainThread();
+
+  void PerformCleanupOnMainThread();
+  void ScheduleMainThreadCleanup();
 
   // When the context is going away, reject any pending script promise
   // resolvers.
@@ -467,6 +469,11 @@ class MODULES_EXPORT BaseAudioContext
   // don't want to call resolve an excessive number of times.
   bool is_resolving_resume_promises_;
 
+  // Set to |true| by the audio thread when it posts a main-thread task to
+  // perform delayed state sync'ing updates that needs to be done on the main
+  // thread. Cleared by the main thread task once it has run.
+  bool has_posted_cleanup_task_;
+
   // Whether a user gesture is required to start this AudioContext.
   bool user_gesture_required_;