Presentation API: Blink changes to allow getAvailability() to be rejected.

public/platform/modules/presentation/WebPresentationClient.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 WebPresentationClient_h
 #define WebPresentationClient_h
 
 #include "public/platform/WebCallbacks.h"
 #include "public/platform/WebCommon.h"
 
 namespace blink {
 
 class WebPresentationAvailabilityObserver;
 class WebPresentationController;
 class WebPresentationSessionClient;
 class WebString;
 struct WebPresentationError;
 
 // If session was created, callback's onSuccess() is invoked with the information about the
 // presentation session created by the embedder. Otherwise, onError() is invoked with the error code
 // and message.
 using WebPresentationSessionClientCallbacks = WebCallbacks<WebPresentationSessionClient, WebPresentationError>;
 
 // Callback for .getAvailability().
-using WebPresentationAvailabilityCallbacks = WebCallbacks<bool, void>;
+using WebPresentationAvailabilityCallbacks = WebCallbacks<bool, WebPresentationError>;
 
 // The implementation the embedder has to provide for the Presentation API to work.
 class WebPresentationClient {
 public:
     virtual ~WebPresentationClient() { }
 
     // Passes the Blink-side delegate to the embedder.
     virtual void setController(WebPresentationController*) = 0;
 
     // Called when the frame requests to start a new session.
@@ skipping 29 matching lines @@
     virtual void startListening(WebPresentationAvailabilityObserver*) = 0;
 
     // Stop listening to changes in presentation displays availability. The
     // observer will no longer be notified in case of a change.
     virtual void stopListening(WebPresentationAvailabilityObserver*) = 0;
 };
 
 } // namespace blink
 
 #endif // WebPresentationClient_h