Undo overlay fullscreen video background transparency

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 88 matching lines @@
     }
 }
 
 void FullscreenController::didExitFullScreen()
 {
     if (!m_fullScreenFrame)
         return;
 
     if (Document* document = m_fullScreenFrame->document()) {
         if (Fullscreen* fullscreen = Fullscreen::fromIfExists(*document)) {
-            if (fullscreen->webkitCurrentFullScreenElement()) {
+            Element* element = fullscreen->webkitCurrentFullScreenElement();
+            if (element) {
                 // When the client exits from full screen we have to call fullyExitFullscreen to notify
                 // the document. While doing that, suppress notifications back to the client.
                 m_isCancelingFullScreen = true;
                 Fullscreen::fullyExitFullscreen(*document);
                 m_isCancelingFullScreen = false;
 
-                if (RuntimeEnabledFeatures::overlayFullscreenVideoEnabled() && m_webViewImpl->layerTreeView())
+                // If the video used overlay fullscreen mode, the background was made transparent. Restore the transparency.
+                if (isHTMLVideoElement(element) && m_webViewImpl->layerTreeView())
                     m_webViewImpl->layerTreeView()->setHasTransparentBackground(m_webViewImpl->isTransparent());
 
                 if (m_exitFullscreenPageScaleFactor) {
                     updatePageScaleConstraints(true);
                     m_webViewImpl->setPageScaleFactor(m_exitFullscreenPageScaleFactor);
                     m_webViewImpl->mainFrame()->setScrollOffset(WebSize(m_exitFullscreenScrollOffset));
                     m_webViewImpl->setVisualViewportOffset(m_exitFullscreenVisualViewportOffset);
                     m_exitFullscreenPageScaleFactor = 0;
                     m_exitFullscreenScrollOffset = IntSize();
                 }
@@ skipping 67 matching lines @@
 }
 
 DEFINE_TRACE(FullscreenController)
 {
     visitor->trace(m_provisionalFullScreenElement);
     visitor->trace(m_fullScreenFrame);
 }
 
 } // namespace blink