media_controls: Add UI for showing a promo bubble on a control button.

third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MediaControlDownloadButtonElement_h
 #define MediaControlDownloadButtonElement_h
 
 #include "core/html/shadow/MediaControlElementTypes.h"
+#include "modules/media_controls/MediaControlsImpl.h"
+#include "modules/media_controls/elements/MediaControlElementsHelper.h"
 
 namespace blink {
 
 class Event;
 class MediaControlsImpl;
 
+class MediaControlDownloadButtonContainer final
+    : public MediaControlDivElement {
+ public:
+  explicit MediaControlDownloadButtonContainer(MediaControlsImpl&);
+  bool KeepEventInNode(Event*) override;
+};
+
 class MediaControlDownloadButtonElement final
     : public MediaControlInputElement {
  public:
   explicit MediaControlDownloadButtonElement(MediaControlsImpl&);
 
   // Returns true if the download button should be shown. We should
   // show the button for only non-MSE, non-EME, and non-MediaStream content.
   bool ShouldDisplayDownloadButton();
 
   // MediaControlInputElement overrides.
@@ skipping 22 matching lines @@
 
   // UMA related boolean. They are used to prevent counting something twice
   // for the same media element.
   bool click_use_counted_ = false;
   bool show_use_counted_ = false;
 };
 
 }  // namespace blink
 
 #endif  // MediaControlDownloadButtonElement_h