chrome/blink: Add functionality for in-product help for media elements.

third_party/WebKit/Source/modules/media_controls/elements/MediaControlElementBase.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 MediaControlElementBase_h
 #define MediaControlElementBase_h
 
 #include "core/dom/Element.h"
+#include "modules/ModulesExport.h"
 #include "modules/media_controls/elements/MediaControlElementType.h"
 #include "platform/heap/GarbageCollected.h"
 #include "platform/heap/Visitor.h"
 #include "public/platform/WebLocalizedString.h"
 
 namespace blink {
 
 class Element;
 class HTMLElement;
 class HTMLMediaElement;
 class MediaControlsImpl;
 
 // MediaControlElementBase is the base class for all the media control elements.
 // It is sub-classed by MediaControlInputElement and MediaControlDivElement
 // which are then used by the final implementations.
-class MediaControlElementBase : public GarbageCollectedMixin {
+class MODULES_EXPORT MediaControlElementBase : public GarbageCollectedMixin {

[mlamouri (slow - plz ping), 2017/07/25 17:29:08]

Why is this required?

  public:
   // These hold the state about whether this control should be shown if
   // space permits.  These will also show / hide as needed.
   virtual void SetIsWanted(bool);
   bool IsWanted() const;
 
   // Tell us whether we fit or not.  This will hide / show the control as
   // needed, also.
   void SetDoesFit(bool);
 
@@ skipping 50 matching lines @@
   Member<MediaControlsImpl> media_controls_;
   MediaControlElementType display_type_;
   Member<HTMLElement> element_;
   bool is_wanted_ : 1;
   bool does_fit_ : 1;
 };
 
 }  // namespace blink
 
 #endif  // MediaControlElementBase_h