Support subtitles for native fullscreen video

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index d2204b62e631cdab5fd099e1337fc6534604b007..0f8038f71c27b088ba17e872dac51447f553269f 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -1999,8 +1999,10 @@ void Document::detach(const AttachContext& context)
     if (page())
         page()->documentDetached(this);
 
-    if (this == topDocument())
+    if (this == topDocument()) {
         clearAXObjectCache();
+        renderView()->setCurrentFullscreenRenderer(0);

[esprehn, 2013/09/20 22:01:09]

We're going to destroy the RenderView right after this (see a few lines down)
which should clear this right?

+    }
 
     stopActiveDOMObjects();
     m_eventQueue->close();