Support subtitles for native fullscreen video

Source/web/FullscreenController.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 65 matching lines @@
 
     if (Document* doc = m_fullScreenFrame->document()) {
         if (FullscreenElementStack::isFullScreen(doc)) {
             if (!m_exitFullscreenPageScaleFactor) {
                 m_exitFullscreenPageScaleFactor = m_webViewImpl->pageScaleFactor();
                 m_exitFullscreenScrollOffset = m_webViewImpl->mainFrame()->scrollOffset();
                 m_webViewImpl->setPageScaleFactorPreservingScrollOffset(1.0f);
             }
 
             FullscreenElementStack::from(doc)->webkitDidEnterFullScreenForElement(0);
+#if USE(NATIVE_FULLSCREEN_VIDEO)
+            if (Element* element = FullscreenElementStack::currentFullScreenElementFrom(doc)) {
+                if (element->isMediaElement() && m_webViewImpl->layerTreeView())
+                    m_webViewImpl->layerTreeView()->setHasTransparentBackground(true);
+            }
+#endif
         }
     }
 }
 
 void FullscreenController::willExitFullScreen()
 {
     if (!m_fullScreenFrame)
         return;
 
     if (Document* doc = m_fullScreenFrame->document()) {
         FullscreenElementStack* fullscreen = FullscreenElementStack::fromIfExists(doc);
         if (!fullscreen)
             return;
         if (fullscreen->isFullScreen(doc)) {
             // When the client exits from full screen we have to call webkitCancelFullScreen to
             // notify the document. While doing that, suppress notifications back to the client.
             m_isCancelingFullScreen = true;
             fullscreen->webkitCancelFullScreen();
             m_isCancelingFullScreen = false;
             fullscreen->webkitWillExitFullScreenForElement(0);
+#if USE(NATIVE_FULLSCREEN_VIDEO)
+            if (m_webViewImpl->layerTreeView())
+                m_webViewImpl->layerTreeView()->setHasTransparentBackground(m_webViewImpl->isTransparent());
+#endif
         }
     }
 }
 
 void FullscreenController::didExitFullScreen()
 {
     if (!m_fullScreenFrame)
         return;
 
     if (Document* doc = m_fullScreenFrame->document()) {
@@ skipping 60 matching lines @@
             mediaElement->player()->exitFullscreen();
         return;
     }
 #endif
     if (WebViewClient* client = m_webViewImpl->client())
         client->exitFullScreen();
 }
 
 }