[Presentation API] 1-UA presentation support + presenter APIs.

content/common/presentation/presentation_service.mojom

Index: content/common/presentation/presentation_service.mojom
diff --git a/content/common/presentation/presentation_service.mojom b/content/common/presentation/presentation_service.mojom
index e201791642a0fc5ccf4128ecf03dff3e1d27e365..157db91e374acbc8e1f6ec6284d7ddd86d64ec38 100644
--- a/content/common/presentation/presentation_service.mojom
+++ b/content/common/presentation/presentation_service.mojom
@@ -104,6 +104,14 @@ interface PresentationService {
   // PresentationServiceClient::OnSessionMessagesReceived.
   // This is called after a presentation session is created.
   ListenForSessionMessages(PresentationSessionInfo sessionInfo);
+
+  // Gets a single receiver PresentationSessionInfo object for the

[miu, 2015/10/07 21:51:47]

See my comment in presentation_service_delegate.h, re: what if a receiver never
becomes available?

[imcheng, 2015/10/10 04:39:43]

since all mojo callbacks have to be invoked before they are destroyed, null will
be returned just before this request becomes invalid. Added comments.

+  // offscreen presentation hosted on the offscreen tab containing this frame.
+  // If the calling frame is not the main frame of an offscreen tab,
+  // null will be returned.
+  // Otherwise, a PresentationSessionInfo object will be returned,
+  // with url set to empty, and id set to the ID of the offscreen presentation.
+  GetPresentationReceiverSession() => (PresentationSessionInfo? session_info);
 };
 
 interface PresentationServiceClient {