Oilpan: handle MediaControls like the GCed object it is.

Source/core/html/shadow/MediaControls.cpp

 /*
  * Copyright (C) 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 51 matching lines @@
     return true;
 }
 
 static bool preferHiddenVolumeControls(const Document& document)
 {
     return !document.settings() || document.settings()->preferHiddenVolumeControls();
 }
 
 class MediaControls::BatchedControlUpdate {
     WTF_MAKE_NONCOPYABLE(BatchedControlUpdate);
+    STACK_ALLOCATED();
 public:
-    BatchedControlUpdate(MediaControls* controls) : m_controls(controls)
+    explicit BatchedControlUpdate(MediaControls* controls)
+        : m_controls(controls)
     {
         ASSERT(isMainThread());
         ASSERT(s_batchDepth >= 0);
         ++s_batchDepth;
     }
     ~BatchedControlUpdate()
     {
         ASSERT(isMainThread());
         ASSERT(s_batchDepth > 0);
         if (!(--s_batchDepth))
             m_controls->computeWhichControlsFit();
     }
 
 private:
-    MediaControls* m_controls;
+    RawPtrWillBeMember<MediaControls> m_controls;
     static int s_batchDepth;
 };
 
 // Count of number open batches for controls visibility.
 int MediaControls::BatchedControlUpdate::s_batchDepth = 0;
 
 MediaControls::MediaControls(HTMLMediaElement& mediaElement)
     : HTMLDivElement(mediaElement.document())
     , m_mediaElement(&mediaElement)
     , m_overlayEnclosure(nullptr)
@@ skipping 648 matching lines @@
     visitor->trace(m_toggleClosedCaptionsButton);
     visitor->trace(m_fullScreenButton);
     visitor->trace(m_durationDisplay);
     visitor->trace(m_enclosure);
     visitor->trace(m_castButton);
     visitor->trace(m_overlayCastButton);
     HTMLDivElement::trace(visitor);
 }
 
 }