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

public/platform/modules/presentation/WebPresentationClient.h

Index: public/platform/modules/presentation/WebPresentationClient.h
diff --git a/public/platform/modules/presentation/WebPresentationClient.h b/public/platform/modules/presentation/WebPresentationClient.h
index 82d740d2c1aa21e0e0fea211f2e5989fa4564e85..9e2b75cf97a253656095d9deea48e9084fa151b2 100644
--- a/public/platform/modules/presentation/WebPresentationClient.h
+++ b/public/platform/modules/presentation/WebPresentationClient.h
@@ -10,6 +10,7 @@
 
 namespace blink {
 
+class WebPresentationAvailabilityObserver;
 class WebPresentationController;
 class WebPresentationSessionClient;
 class WebString;
@@ -20,6 +21,9 @@ struct WebPresentationError;
 // 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:
@@ -53,6 +57,25 @@ public:
 
     // 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 device to present.

[whywhat, 2015/07/02 22:32:38]

nit: s/device to present/presentation display/

[mlamouri (slow - plz ping), 2015/07/03 13:58:26]

Done.

+    // 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 = false;
+        callbacks->onSuccess(&result);
+        delete callbacks;
+    }
+
+    // Start listening to presentation device availabilities. The observer will

[whywhat, 2015/07/02 22:32:38]

nit: s/presentation device availabilities/changes in presentation displays
availability/

[mlamouri (slow - plz ping), 2015/07/03 13:58:27]

Done.

+    // be notified in case of a change. The observer is respensible to call
+    // stopListening() before being destroyed.
+    virtual void startListening(WebPresentationAvailabilityObserver*) {}

[whywhat, 2015/07/02 22:32:38]

don't you need to pass a url here too?

[mlamouri (slow - plz ping), 2015/07/03 13:58:26]

I guess we could but we wouldn't use it anyway. Given the future changes we are
going to do, I think we should keep this to a minimum.

+
+    // Stop listening to presentation device availabilities. The observer will

[whywhat, 2015/07/02 22:32:38]

ditto

[mlamouri (slow - plz ping), 2015/07/03 13:58:27]

Done.

+    // no longer be notified in case of a change.
+    virtual void stopListening(WebPresentationAvailabilityObserver*) {}

[whywhat, 2015/07/02 22:32:38]

ditto

[mlamouri (slow - plz ping), 2015/07/03 13:58:26]

See above.

 };
 
 } // namespace blink