Notify WebMediaPlayer when its ancestor enters/exists fullscreen.

third_party/WebKit/Source/core/html/HTMLMediaElement.h

Index: third_party/WebKit/Source/core/html/HTMLMediaElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLMediaElement.h b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
index a5fd674d44729cc1f010fcbc5a197f5c2db339b4..599b51c5affb47bd19b638de15c7fec01cc7f8cf 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
@@ -33,6 +33,7 @@
 #include "core/CoreExport.h"
 #include "core/dom/ActiveDOMObject.h"
 #include "core/dom/ExceptionCode.h"
+#include "core/dom/Fullscreen.h"
 #include "core/events/GenericEventQueue.h"
 #include "core/html/AutoplayExperimentHelper.h"
 #include "core/html/HTMLElement.h"
@@ -79,6 +80,7 @@ class CORE_EXPORT HTMLMediaElement : public HTMLElement,
                                      public Supplementable<HTMLMediaElement>,
                                      public ActiveScriptWrappable,
                                      public ActiveDOMObject,
+                                     public Fullscreen::FullscreenObserver,
                                      private WebMediaPlayerClient {
   DEFINE_WRAPPERTYPEINFO();
   USING_GARBAGE_COLLECTED_MIXIN(HTMLMediaElement);
@@ -360,6 +362,10 @@ class CORE_EXPORT HTMLMediaElement : public HTMLElement,
   void setReadyState(ReadyState);
   void setNetworkState(WebMediaPlayer::NetworkState);
 
+  // Fullscreen::FullscreenObserver implementation.
+  void onEnteredFullscreen() override;
+  void onExitedFullscreen() override;
+
   // WebMediaPlayerClient implementation.
   void networkStateChanged() final;
   void readyStateChanged() final;