[Presentation API / Media Router] Clean up default pres URL logic.

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 3256a965c6fcfc4a0ed9c6901ae5d9895967f1c7..422ae5874d4d1a572136a7dadaf5557a824e8f4d 100644
--- a/content/common/presentation/presentation_service.mojom
+++ b/content/common/presentation/presentation_service.mojom
@@ -42,12 +42,14 @@ struct SessionMessage {
 };
 
 interface PresentationService {
-  // Called when the frame sets or changes the default presentation URL.
-  SetDefaultPresentationURL(string url);
-
   // Sets the PresentationServiceClient.
   SetClient(PresentationServiceClient client);
 
+  // Called when the frame sets or changes the default presentation URL.
+  // When the default presentation is started on this frame,
+  // PresentationServiceClient::OnDefaultSessionStarted will be invoked.
+  SetDefaultPresentationURL(string url);
+
   // Starts listening for screen availability for presentation of
   // |url|. Availability results will be returned to the client via
   // PresentationServiceClient::OnScreenAvailabilityUpdated.
@@ -58,13 +60,6 @@ interface PresentationService {
   // |url|.
   StopListeningForScreenAvailability(string url);
 
-  // Called when the renderer is ready to receive the browser initiated
-  // session. If the default session is started by the embedder before this
-  // call, the embedder may queue it and run the callback when the call is
-  // performed.
-  ListenForDefaultSessionStart()
-      => (PresentationSessionInfo? defaultSessionInfo);
-
   // Called when startSession() is called by the frame. The result callback
   // will return a non-null and valid PresentationSessionInfo if starting the
   // session succeeded, or null with a PresentationError if starting the
@@ -89,7 +84,8 @@ interface PresentationService {
   // The false in the result callback notifies the renderer to stop sending
   // the send requests and invalidate all pending requests. This occurs
   // for eg., when frame is deleted or navigated away.
-  SendSessionMessage(PresentationSessionInfo sessionInfo, SessionMessage message_request) => (bool success);
+  SendSessionMessage(PresentationSessionInfo sessionInfo,
+                     SessionMessage message_request) => (bool success);
 
   // Called when closeSession() is called by the frame.
   CloseSession(string presentation_url, string presentation_id);
@@ -125,5 +121,9 @@ interface PresentationServiceClient {
                         PresentationConnectionState newState);
 
   // See PresentationService::ListenForSessionMessages.
-  OnSessionMessagesReceived(PresentationSessionInfo sessionInfo, array<SessionMessage> messages);
-}; 
+  OnSessionMessagesReceived(PresentationSessionInfo sessionInfo,
+                            array<SessionMessage> messages);
+
+  // See PresentationService::SetDefaultPresentationURL.
+  OnDefaultSessionStarted(PresentationSessionInfo sessionInfo);
+};