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

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

Index: third_party/WebKit/Source/core/html/shadow/MediaControls.h
diff --git a/third_party/WebKit/Source/core/html/shadow/MediaControls.h b/third_party/WebKit/Source/core/html/shadow/MediaControls.h
index 74805310d50a486754080001c24d9494b9eecfb0..356742286a098a9f140a52e5bc02944f05f72396 100644
--- a/third_party/WebKit/Source/core/html/shadow/MediaControls.h
+++ b/third_party/WebKit/Source/core/html/shadow/MediaControls.h
@@ -41,11 +41,17 @@ class ShadowRoot;
 class CORE_EXPORT MediaControls final : public HTMLDivElement {
  public:
   static MediaControls* create(HTMLMediaElement&, ShadowRoot&);
+  ~MediaControls() override;
 
   HTMLMediaElement& mediaElement() const { return *m_mediaElement; }
 
   void reset();
 
+  // Called when the HTMLMediaElement is no longer in the document to the
+  // MediaControls instance can be ready to be garbage collected by removing
+  // event listeners.
+  void detach();
+
   void show();
   void hide();
   bool isVisible() const;