Add download button to MediaDocument on Android.

third_party/WebKit/Source/core/html/MediaDocument.h

 /*
  * Copyright (C) 2008,2009 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 19 matching lines @@
 
 namespace blink {
 
 class MediaDocument final : public HTMLDocument {
 public:
     static PassRefPtrWillBeRawPtr<MediaDocument> create(const DocumentInit& initializer = DocumentInit())
     {
         return adoptRefWillBeNoop(new MediaDocument(initializer));
     }
 
+    void updateLayout();
+
 private:
     MediaDocument(const DocumentInit&);
 
     PassRefPtrWillBeRawPtr<DocumentParser> createParser() override;
 
     void defaultEventHandler(Event*) override;
 };
 
 } // namespace blink
 
 #endif