Implement <video controls> dodging for text track layout

Source/core/html/track/TextTrackContainer.h

 /*
  * Copyright (C) 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2012 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
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 #include "core/html/HTMLDivElement.h"
 
 namespace blink {
 
 class HTMLMediaElement;
 
 class TextTrackContainer final : public HTMLDivElement {
 public:
     static PassRefPtrWillBeRawPtr<TextTrackContainer> create(Document&);
 
-    void updateDisplay(HTMLMediaElement&);
+    // Runs the "rules for updating the text track rendering". The
+    // ExposingControls enum is used in the WebVTT processing model to reset the
+    // layout when the media controls become visible, to avoid overlapping them.
+    enum ExposingControls {
+        DidNotStartExposingControls,
+        DidStartExposingControls
+    };
+    void updateDisplay(HTMLMediaElement&, ExposingControls);
 
 private:
     TextTrackContainer(Document&);
 
     virtual bool isTextTrackContainer() const override { return true; }
 
     virtual LayoutObject* createLayoutObject(const LayoutStyle&) override;
 };
 
 DEFINE_ELEMENT_TYPE_CASTS(TextTrackContainer, isTextTrackContainer());
 
 } // namespace blink
 
 #endif // TextTrackContainer_h