Reviewed by Dan Bernstein & Simon Fraser.

        <rdar://problem/7297717>
        https://bugs.webkit.org/show_bug.cgi?id=30323
        Play/pause button in full-screen video controller does not reflect current state

        * WebView/WebVideoFullscreenController.mm:
        (-[WebVideoFullscreenController setMediaElement:WebCore::]): Register for QTMovieRateDidChangeNotification
        (-[WebVideoFullscreenController rateChanged:]): Call HUD controller when rate changes.

        * WebView/WebVideoFullscreenHUDWindowController.h:
        * WebView/WebVideoFullscreenHUDWindowController.mm:
        (-[WebVideoFullscreenHUDWindowController scheduleTimeUpdate]): Call updateRate so play button
        reflects playback state.
        (-[WebVideoFullscreenHUDWindowController updateRate]): New, set play button state according to
        movie state.
        (-[WebVideoFullscreenHUDWindowController playingChanged:]): Only call [self playing] once.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@49948 268f45cc-cd09-0410-ab3c-d52691b4dbfc