Pass origin to StartObservingMediaSinks.

chrome/browser/media/router/media_router.mojom

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module media_router.interfaces;
 
 // Represents an output sink to which media can be routed.
 struct MediaSink {
   enum IconType {
     CAST,
@@ skipping 157 matching lines @@
   // Sends |message| via the media route |media_route_id|.
   // If the operation was successful, |sent| is true; otherwise it is false.
   SendRouteMessage(string media_route_id, string message) => (bool sent);
 
   // Sends |data| via the media route |media_route_id|.
   // If the operation was successful, |sent| is true; otherwise it is false.
   SendRouteBinaryMessage(string media_route_id, array<uint8> data)
       => (bool sent);
 
   // Starts querying for sinks capable of displaying |media_source|.
-  StartObservingMediaSinks(string media_source);
+  // |origin| can be used to validate the media sink query to prevent

[mark a. foltz, 2016/02/17 21:50:51]

Maybe just say "to optionally verify that the origin is authorized to issue the
query."

[matt.boetger, 2016/02/18 00:50:33]

Done.

+  // fingerprinting by nefarious origins.
+  StartObservingMediaSinks(string media_source, string origin);
 
   // Stops querying sinks for |media_source|.
   StopObservingMediaSinks(string media_source);
 
   // Starts reporting the state of active media routes via
   // OnRoutesUpdated() in the context of the |media_source|.  The
   // |media_source| represents the application interested in the media
   // routes (usually the web page from which the content originates).
   // If no |media_source| is given, this should be considered an
   // observer that is not associated with a media source, and thus
@@ skipping 59 matching lines @@
     TERMINATED
   };
 
   // Registers a MediaRouteProvider with the MediaRouter.
   // Returns a string that uniquely identifies the Media Router browser
   // process.
   RegisterMediaRouteProvider(MediaRouteProvider media_router_provider) =>
       (string instance_id);
 
   // Called when the Media Route Manager receives a new list of sinks.
   OnSinksReceived(string media_source, array<MediaSink> sinks);

[imcheng, 2016/02/16 20:54:18]

do we need an origin param here?

 
   // Called when issues are reported for media routes.
   OnIssue(Issue issue);
 
   // Called when list of routes has been updated in the context of the
   // calling |media_source|.  The array |joinable_route_ids| should
   // contain route IDs of joinable routes found in the |routes| array.
   OnRoutesUpdated(array<MediaRoute> routes, string media_source,
       array<string> joinable_route_ids);
 
   // Called when the overall availability of media sinks has been updated.
   OnSinkAvailabilityUpdated(SinkAvailability availability);
 
   // Called when the state of presentation connected to route |route_id| has
   // changed to |state|.
   OnPresentationConnectionStateChanged(
       string route_id, PresentationConnectionState state);
 };