Add UseCounter features for Document prefixed fullscreen APIs

Since the unprefixed API isn't event implemented yet removal is nowhere
in sight, but it's still interesting to track these features over time.

BUG=none

Review URL: https://codereview.chromium.org/214873002

git-svn-id: svn://svn.chromium.org/blink/trunk@170270 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/dom/DocumentFullscreen.idl

@@ -21,13 +21,13 @@
 
 partial interface Document {
     // Mozilla version
-    readonly attribute boolean webkitIsFullScreen;
-    readonly attribute boolean webkitFullScreenKeyboardInputAllowed;
-    readonly attribute Element webkitCurrentFullScreenElement;
-    void webkitCancelFullScreen();
+    [MeasureAs=PrefixedDocumentIsFullscreen] readonly attribute boolean webkitIsFullScreen;
+    [MeasureAs=PrefixedDocumentFullScreenKeyboardInputAllowed] readonly attribute boolean webkitFullScreenKeyboardInputAllowed;
+    [MeasureAs=PrefixedDocumentCurrentFullScreenElement] readonly attribute Element webkitCurrentFullScreenElement;
+    [MeasureAs=PrefixedDocumentCancelFullScreen] void webkitCancelFullScreen();
 
     // W3C version
-    readonly attribute boolean webkitFullscreenEnabled;
-    readonly attribute Element webkitFullscreenElement;
-    void webkitExitFullscreen();
+    [MeasureAs=PrefixedDocumentFullscreenEnabled] readonly attribute boolean webkitFullscreenEnabled;
+    [MeasureAs=PrefixedDocumentFullscreenElement] readonly attribute Element webkitFullscreenElement;
+    [MeasureAs=PrefixedDocumentExitFullscreen] void webkitExitFullscreen();
 };

third_party/WebKit/Source/core/frame/UseCounter.h

@@ -332,6 +332,13 @@ public:
         PrefixedAllowFullscreenAttribute = 315,
         XHRProgressEventPosition = 316,
         XHRProgressEventTotalSize = 317,
+        PrefixedDocumentIsFullscreen = 318,
+        PrefixedDocumentFullScreenKeyboardInputAllowed = 319,
+        PrefixedDocumentCurrentFullScreenElement = 320,
+        PrefixedDocumentCancelFullScreen = 321,
+        PrefixedDocumentFullscreenEnabled = 322,
+        PrefixedDocumentFullscreenElement = 323,
+        PrefixedDocumentExitFullscreen = 324,
         // Add new features immediately above this line. Don't change assigned
         // numbers of any item, and don't reuse removed slots.
         NumberOfFeatures, // This enum value must be last.