[Presentation API] Plumbing the |defaultpresentationstart| event from Blink to browser/Mojo.

content/renderer/presentation/presentation_dispatcher.cc

Index: content/renderer/presentation/presentation_dispatcher.cc
diff --git a/content/renderer/presentation/presentation_dispatcher.cc b/content/renderer/presentation/presentation_dispatcher.cc
index 88236345a26ab374f4a9fdc7ca6ee917ba8fb7b5..841338f1eb3b7620c0974e1d2fdcae10b32c9f7d 100644
--- a/content/renderer/presentation/presentation_dispatcher.cc
+++ b/content/renderer/presentation/presentation_dispatcher.cc
@@ -113,6 +113,24 @@ void PresentationDispatcher::OnScreenAvailabilityChanged(bool available) {
   controller_->didChangeAvailability(available);
 }
 
+void PresentationDispatcher::OnDefaultPresentationStarted(
+    presentation::PresentationSessionInfoPtr session_info) {
+  if (!controller_)
+    return;
+
+  // Reset the callback to get the next event.
+  presentation_service_->ListenForDefaultPresentationStart(base::Bind(
+      &PresentationDispatcher::OnDefaultPresentationStarted,
+      base::Unretained(this)));
+
+  DCHECK(!session_info.is_null());
+  PresentationSessionDispatcher* session_dispatcher =
+      new PresentationSessionDispatcher(session_info.Pass());
+  presentation_session_dispatchers_.push_back(session_dispatcher);
+  controller_->didStartDefaultPresentation(
+      new PresentationSessionClient(session_dispatcher));
+}
+
 void PresentationDispatcher::OnSessionCreated(
     blink::WebPresentationSessionClientCallbacks* callback,
     presentation::PresentationSessionInfoPtr session_info,
@@ -139,6 +157,9 @@ void PresentationDispatcher::ConnectToPresentationServiceIfNeeded() {
 
   render_frame()->GetServiceRegistry()->ConnectToRemoteService(
       &presentation_service_);
+  presentation_service_->ListenForDefaultPresentationStart(base::Bind(
+      &PresentationDispatcher::OnDefaultPresentationStarted,
+      base::Unretained(this)));
 }
 
 }  // namespace content