Presentation API: implement .getAvalability() (Blink side).

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>;
+
 // 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 attaches the first event listener to or removes the
     // last event listener from the |availablechange| event.
@@ skipping 13 matching lines @@
     // Called when the frame requests to send ArrayBuffer/View data to an existing session.
     // Embedder copies the |data| and the ownership is not transferred.
     virtual void sendArrayBuffer(const WebString& presentationUrl, const WebString& presentationId, const uint8_t* data, size_t length) = 0;
 
     // Called when the frame requests to send Blob data to an existing session.
     // Embedder copies the |data| and the ownership is not transferred.
     virtual void sendBlobData(const WebString& presentationUrl, const WebString& presentationId, const uint8_t* data, size_t length) = 0;
 
     // Called when the frame requests to close an existing session.
     virtual void closeSession(const WebString& url, const WebString& presentationId) = 0;
+
+    // Called when the frame wants to know the availability of a presentation
+    // display.
+    // The ownership of the |callbacks| argument is transferred to the embedder.
+    virtual void getAvailability(const WebString& url, WebPresentationAvailabilityCallbacks* callbacks)
+    {
+        // TODO(mlamouri): remove when implemented in Chromium.
+        bool* result = new bool(false);
+        callbacks->onSuccess(result);
+        delete callbacks;
+    }
+
+    // Start listening to changes in presentation displays availability. The
+    // observer will be notified in case of a change. The observer is
+    // respensible to call stopListening() before being destroyed.
+    virtual void startListening(WebPresentationAvailabilityObserver*) {}
+
+    // Stop listening to changes in presentation displays availability. The
+    // observer will no longer be notified in case of a change.
+    virtual void stopListening(WebPresentationAvailabilityObserver*) {}
 };
 
 } // namespace blink
 
 #endif // WebPresentationClient_h