Presentation API: allow the Mojo service to reject a getAvailability() call.

content/renderer/presentation/presentation_dispatcher.cc

 // 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.
 
 #include "content/renderer/presentation/presentation_dispatcher.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/logging.h"
@@ skipping 330 matching lines @@
 
 void PresentationDispatcher::OnScreenAvailabilityUpdated(bool available) {
   last_known_availability_ = available;
 
   if (listening_state_ == ListeningState::Waiting)
     listening_state_ = ListeningState::Active;
 
   for (auto observer : availability_observers_)
     observer->availabilityChanged(available);
 
+  for (auto observer : availability_observers_)
+    observer->availabilityChanged(available);
+
   for (AvailabilityCallbacksMap::iterator iter(&availability_callbacks_);
        !iter.IsAtEnd(); iter.Advance()) {
     iter.GetCurrentValue()->onSuccess(new bool(available));
   }
   availability_callbacks_.Clear();
 
   UpdateListeningState();
 }
 
+void PresentationDispatcher::OnScreenAvailabilityNotSupported() {
+  DCHECK(listening_state_ == ListeningState::Waiting);
+
+  for (AvailabilityCallbacksMap::iterator iter(&availability_callbacks_);
+       !iter.IsAtEnd(); iter.Advance()) {
+    iter.GetCurrentValue()->onError(new blink::WebPresentationError(
+        blink::WebPresentationError::ErrorTypeAvailabilityNotSupported,
+        blink::WebString::fromUTF8(
+            "getAvailability() isn't supported at the moment. It can be due to"
+            "a permanent or temporary system limitation. It is recommended to"
+            "try to blindly start a session in that case.")));
+  }
+  availability_callbacks_.Clear();
+
+  UpdateListeningState();
+}
+
 void PresentationDispatcher::OnDefaultSessionStarted(
     presentation::PresentationSessionInfoPtr session_info) {
   if (!controller_)
     return;
 
   // Reset the callback to get the next event.
   presentation_service_->ListenForDefaultSessionStart(base::Bind(
       &PresentationDispatcher::OnDefaultSessionStarted,
       base::Unretained(this)));
 
@@ skipping 86 matching lines @@
   if (should_listen) {
     listening_state_ = ListeningState::Waiting;
     presentation_service_->ListenForScreenAvailability();
   } else {
     listening_state_ = ListeningState::Inactive;
     presentation_service_->StopListeningForScreenAvailability();
   }
 }
 
 }  // namespace content