[Media, Controls] Cleanup resize observer before dereferencing.

third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.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 425 matching lines @@
   DCHECK(!MediaElement().isConnected());
 
   // TODO(mlamouri): we hide show the controls instead of having
   // HTMLMediaElement do it.
 
   window_event_listener_->Stop();
   media_event_listener_->Detach();
   if (orientation_lock_delegate_)
     orientation_lock_delegate_->Detach();
 
-  resize_observer_.Clear();
+  if (resize_observer_) {
+    resize_observer_->disconnect();
+    resize_observer_.Clear();
+  }
 }
 
 void MediaControlsImpl::Reset() {
   EventDispatchForbiddenScope::AllowUserAgentEvents allow_events_in_shadow;
   BatchedControlUpdate batch(this);
 
   const double duration = MediaElement().duration();
   duration_display_->setTextContent(
       LayoutTheme::GetTheme().FormatMediaControlsTime(duration));
   duration_display_->SetCurrentValue(duration);
@@ skipping 679 matching lines @@
   visitor->Trace(cast_button_);
   visitor->Trace(overlay_cast_button_);
   visitor->Trace(media_event_listener_);
   visitor->Trace(window_event_listener_);
   visitor->Trace(orientation_lock_delegate_);
   MediaControls::Trace(visitor);
   HTMLDivElement::Trace(visitor);
 }
 
 }  // namespace blink