Notify WebMediaPlayer when HTML video enters full screen.

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 2505616af94ea7ca993426a45f40c022475b1f5b..11f088c39a00e0534efc6db11e4ffa15ed0ff1a4 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.h
@@ -278,6 +278,12 @@ public:
     WebRemotePlaybackClient* remotePlaybackClient() { return m_remotePlaybackClient; }
     void setRemotePlaybackClient(WebRemotePlaybackClient*);
 
+    // Inform whether the media is in full screen. The media could be in full
+    // screen because either the element itself or its parent element enters
+    // full screen.
+    void updateMediaInFullscreen(bool isFullscreen);
+    bool isMediaInFullscreen() const { return m_isMediaInFullscreen; }
+
 protected:
     HTMLMediaElement(const QualifiedName&, Document&);
     ~HTMLMediaElement() override;
@@ -685,6 +691,10 @@ private:
     Member<ElementVisibilityObserver> m_autoplayVisibilityObserver;
 
     static URLRegistry* s_mediaStreamRegistry;
+
+    // Indicates whether the media is in full screen. When this is true, either
+    // the element itself or its parent element is full screen element.
+    bool m_isMediaInFullscreen;
 };
 
 inline bool isHTMLMediaElement(const HTMLElement& element)