Add UseCounters for prefixed HTMLVideoElement APIs

Source/core/html/HTMLVideoElement.h

Index: Source/core/html/HTMLVideoElement.h
diff --git a/Source/core/html/HTMLVideoElement.h b/Source/core/html/HTMLVideoElement.h
index f9537c8b52389cad3a84b53ebeaae5128f8672af..d2a7732304173f858a5880ee5bbba0d00153ba8d 100644
--- a/Source/core/html/HTMLVideoElement.h
+++ b/Source/core/html/HTMLVideoElement.h
@@ -27,6 +27,7 @@
 #define HTMLVideoElement_h
 
 #include "core/html/HTMLMediaElement.h"
+#include "core/page/UseCounter.h"
 
 namespace WebCore {
 
@@ -45,15 +46,17 @@ public:
     unsigned videoHeight() const;
 
     // Fullscreen
-    void webkitEnterFullscreen(ExceptionState&);
-    void webkitExitFullscreen();
+    void webkitEnterFullscreen(ExceptionState&, UseCounter::Feature);
+    void webkitExitFullscreen(UseCounter::Feature);
+    void webkitEnterFullscreen(ExceptionState& es) { webkitEnterFullscreen(es, UseCounter::PrefixedVideoEnterFullscreen); }
+    void webkitExitFullscreen() { webkitExitFullscreen(UseCounter::PrefixedVideoExitFullscreen); }
     bool webkitSupportsFullscreen();
     bool webkitDisplayingFullscreen();
 
     // FIXME: Maintain "FullScreen" capitalization scheme for backwards compatibility.
     // https://bugs.webkit.org/show_bug.cgi?id=36081
-    void webkitEnterFullScreen(ExceptionState& es) { webkitEnterFullscreen(es); }
-    void webkitExitFullScreen() { webkitExitFullscreen(); }
+    void webkitEnterFullScreen(ExceptionState& es) { webkitEnterFullscreen(es, UseCounter::PrefixedVideoEnterFullScreen); }
+    void webkitExitFullScreen() { webkitExitFullscreen(UseCounter::PrefixedVideoExitFullScreen); }
 
     // Statistics
     unsigned webkitDecodedFrameCount() const;