Media: fix memory leak because of the document holding on an EventListener.

third_party/WebKit/Source/core/html/shadow/MediaControlsOrientationLockDelegate.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MediaControlsOrientationLockDelegate_h
 #define MediaControlsOrientationLockDelegate_h
 
 #include "core/CoreExport.h"
 #include "core/events/EventListener.h"
 #include "public/platform/modules/screen_orientation/WebScreenOrientationLockType.h"
@@ skipping 25 matching lines @@
 // - PendingMetadata => MaybeLockedFullscreen: on loadedmetadata;
 // - PendingMetadata => PendingFullscreen: on fullscreenchange event (leaving
 //   fullscreen);
 // - MaybeLockedFullscreen => PendingFullscreen: on fullscreenchange event
 //   (leaving fullscreen).
 class CORE_EXPORT MediaControlsOrientationLockDelegate final
     : public EventListener {
  public:
   explicit MediaControlsOrientationLockDelegate(HTMLVideoElement&);
 
+  // Called by MediaControls when the HTMLMediaElement is added to a document
+  // document. All event listeners should be added.
+  void attach();
+
+  // Called by MediaControls when the HTMLMediaElement is no longer in the
+  // document. All event listeners should be removed in order to prepare the
+  // object to be garbage collected.
+  void detach();
+
   // EventListener implementation.
   bool operator==(const EventListener&) const override;
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   friend class MediaControlsOrientationLockDelegateTest;
 
   enum class State {
     PendingFullscreen,
@@ skipping 28 matching lines @@
   // In other words, whether the orientation was locked.
   bool m_shouldUnlockOrientation = false;
 
   // `m_videoElement` owns MediaControls that owns |this|.
   Member<HTMLVideoElement> m_videoElement;
 };
 
 }  // namespace blink
 
 #endif  // MediaControlsOrientationLockDelegate_h