Plumbing from WebPresentationClient to the Presentation Mojo service for

content/common/presentation/presentation_service.mojom

+// 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.
+
+module presentation;
+
+interface PresentationService {
+  // Called when there's at least one listener for the |availablechange| event
+  // and the client is ready to process the result. To get the subsequent event
+  // the client has to call the method again when it's ready.
+  // Might start the presentation screens discovery. The discovery might be
+  // stopped by the service implementation if there's no active calls to get
+  // screens availability at the moment.
+  GetScreenAvailability() => (bool available);

[mlamouri (slow - plz ping), 2015/01/26 10:26:39]

If my understanding is correct, you might miss results with this design. Is that
not an issue?

[whywhat, 2015/01/26 11:06:08]

See my reply earlier: I don't think we care about the website getting all the
states in order, just the final one. As I see it, the Mojo service doesn't have
to queue the events but simply store the last known value and pass it to the
callback if there was a change since the last callback was called.

+};