[Reland] Support listening for available screens for multiple

content/renderer/presentation/presentation_dispatcher.h

 // Copyright 2015 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 CONTENT_RENDERER_PRESENTATION_PRESENTATION_DISPATCHER_H_
 #define CONTENT_RENDERER_PRESENTATION_PRESENTATION_DISPATCHER_H_
 
+#include "base/compiler_specific.h"
+#include "content/common/content_export.h"
 #include "content/common/presentation/presentation_service.mojom.h"
 #include "content/public/renderer/render_frame_observer.h"
 #include "third_party/WebKit/public/platform/modules/presentation/WebPresentationClient.h"
 
 namespace content {
 
 // PresentationDispatcher is a delegate for Presentation API messages used by
 // Blink. It forwards the calls to the Mojo PresentationService.
-class PresentationDispatcher
+class CONTENT_EXPORT PresentationDispatcher
     : public RenderFrameObserver,
-      public blink::WebPresentationClient {
+      public NON_EXPORTED_BASE(blink::WebPresentationClient) {
  public:
   explicit PresentationDispatcher(RenderFrame* render_frame);
   ~PresentationDispatcher() override;
 
  private:
   // WebPresentationClient implementation.
   virtual void setController(
       blink::WebPresentationController* controller);
   virtual void updateAvailableChangeWatched(bool watched);
 
   void OnScreenAvailabilityChanged(bool available);
 
   void ConnectToPresentationServiceIfNeeded();
 
   // Used as a weak reference. Can be null since lifetime is bound to the frame.
   blink::WebPresentationController* controller_;
   presentation::PresentationServicePtr presentation_service_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_PRESENTATION_PRESENTATION_DISPATCHER_H_