[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 d46981da9318da22e89bbc2ac0d44a5fc77c4f9e..05ebcced3d91debd1dfd0851060ac0122431125b 100644
--- a/content/common/presentation/presentation_service.mojom
+++ b/content/common/presentation/presentation_service.mojom
@@ -104,6 +104,13 @@ interface PresentationService {
   // PresentationServiceClient::OnSessionMessagesReceived.
   // This is called after a presentation session is created.
   ListenForSessionMessages(PresentationSessionInfo sessionInfo);
+
+  // Gets a single presenter PresentationSessionInfo object for the 1-UA
+  // presentation that was presented onto this frame.
+  // If the calling frame is not a presenter frame, null will be returned.
+  // Otherwise, a presenter PresentationSessionInfo object will be returned,
+  // with url set to empty, and id set to the Id of the 1-UA presentation.
+  GetPresenterSession() => (PresentationSessionInfo? session_info);
 };
 
 interface PresentationServiceClient {