[Media Router] Implement JoinRoute + update CreateRoute API.

chrome/browser/media/router/media_router.h

Index: chrome/browser/media/router/media_router.h
diff --git a/chrome/browser/media/router/media_router.h b/chrome/browser/media/router/media_router.h
index 0699d3f86bf8c26371cc08a93a19e59f515572da..f6f89f23b9d4c401860f95670b223081339a9151 100644
--- a/chrome/browser/media/router/media_router.h
+++ b/chrome/browser/media/router/media_router.h
@@ -29,6 +29,9 @@ class MediaSinksObserver;
 using MediaRouteResponseCallback =
     base::Callback<void(scoped_ptr<MediaRoute>, const std::string&)>;
 
+// Used in cases where a tab ID is not applicable in CreateRoute/JoinRoute.
+const int kInvalidTabId = -1;
+
 // An interface for handling resources related to media routing.
 // Responsible for registering observers for receiving sink availability
 // updates, handling route requests/responses, and operating on routes (e.g.
@@ -38,11 +41,30 @@ class MediaRouter {
   virtual ~MediaRouter() {}
 
   // Creates a media route from |source_id| to |sink_id|.
+  // |origin| and |tab_id| are used for enforcing same-origin and/or same-tab
+  // scope, and are optional.

[mark a. foltz, 2015/06/10 23:18:51]

Since this API is for creating a new route, it's a little confusing to say
"same-origin" or "same-tab" - same with respect to what other origin or tab?

IIUC these values are actually for the provider to enforce these constraints on
JoinRoute() requests.

Can you elaborate the documentation to clarify a bit?

[imcheng (use chromium acct), 2015/06/11 22:49:12]

Ok, I added some comments on the values of |origin| and |tab_id|. Also clarified
the join case with example.

+  // The caller may pass in empty GURL for |origin| and/or |kInvalidTabId| for
+  // |tab_id| if not enforcing same-origin and/or same-tab scope.

[mark a. foltz, 2015/06/10 23:18:51]

The caller doesn't know if the provider is going to enforce this or not - so
should they be mandatory?

[imcheng (use chromium acct), 2015/06/11 22:49:12]

Good point. We can make them mandatory. I left the option to pass -1 for tab_id
for the Chrome apps use case.

   // |callback| is invoked with a response indicating success or failure.
   virtual void CreateRoute(const MediaSource::Id& source_id,
                            const MediaSink::Id& sink_id,
+                           const GURL& origin,
+                           int tab_id,
                            const MediaRouteResponseCallback& callback) = 0;
 
+  // Joins an existing route identified by |presentation_id|.
+  // |source|: The source to route to the existing route.
+  // |presentation_id|: Presentation ID of the existing route.
+  // |origin|, |tab_id|: Origin and tab of the join route request. Used for
+  // validation when enforcing same-origin and/or same-tab scope, and
+  // are optional. (See CreateRoute documentation).

[mark a. foltz, 2015/06/10 23:18:51]

Similar comment about mandatory vs optional for origin, tab_id

[imcheng (use chromium acct), 2015/06/11 22:49:12]

Done.

+  // |callback| is invoked with a response indicating success or failure.
+  virtual void JoinRoute(const MediaSource::Id& source,
+                         const std::string& presentation_id,
+                         const GURL& origin,
+                         int tab_id,
+                         const MediaRouteResponseCallback& callback) = 0;
+
   // Closes the media route specified by |route_id|.
   virtual void CloseRoute(const MediaRoute::Id& route_id) = 0;