[Reland] Support listening for available screens for multiple

content/public/browser/presentation_service_delegate.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_PUBLIC_BROWSER_PRESENTATION_SERVICE_DELEGATE_H_
 #define CONTENT_PUBLIC_BROWSER_PRESENTATION_SERVICE_DELEGATE_H_
 
+#include "content/common/content_export.h"
+
 namespace content {
 
 class PresentationScreenAvailabilityListener;
 
 // An interface implemented by embedders to handle presentation API calls
 // forwarded from PresentationServiceImpl.
-class PresentationServiceDelegate {
+class CONTENT_EXPORT PresentationServiceDelegate {
  public:
   // Observer interface to listen for changes to PresentationServiceDelegate.
-  class Observer {
+  class CONTENT_EXPORT Observer {
    public:
     // Called when the PresentationServiceDelegate is being destroyed.
     virtual void OnDelegateDestroyed() = 0;
 
    protected:
     virtual ~Observer() {}
   };
 
+  virtual ~PresentationServiceDelegate() {}
+
   // Registers an observer with this class to listen for updates to this class.
   // This class does not own the observer.
   // It is an error to add an observer if it has already been added before.
   virtual void AddObserver(Observer* observer) = 0;
   // Unregisters an observer with this class.
   virtual void RemoveObserver(Observer* observer) = 0;
 
   // Registers |listener| to continuously listen for
   // availability updates for a presentation URL, originated from the frame
   // given by |render_process_id| and |render_frame_id|.
@@ skipping 12 matching lines @@
   virtual void RemoveScreenAvailabilityListener(
       int render_process_id,
       int render_frame_id,
       PresentationScreenAvailabilityListener* listener) = 0;
 
   // Unregisters all listeners associated with the frame given by
   // |render_process_id| and |render_frame_id|.
   virtual void RemoveAllScreenAvailabilityListeners(
       int render_process_id,
       int render_frame_id) = 0;
-
- protected:
-  virtual ~PresentationServiceDelegate() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_PRESENTATION_SERVICE_DELEGATE_H_