[Media Router] Wiring for searching route providers for new sinks.

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 245 matching lines @@
 
   // Called when there are no more listeners for messages for |route_id|.
   // Calling this will resolve the pending |ListenForRouteMessages| callback
   // with an empty list.
   StopListeningForRouteMessages(string route_id);
 
   // Indicates that a PresentationConnection that was connected to route
   // |route_id| has been closed (via .close(), garbage collection or
   // navigation).
   DetachRoute(string route_id);
+
+  // Indicates that the Media Router is interested in finding a sink with id
+  // |sink_id| that is compatible with the source urn |media_source|.

[amp, 2016/03/16 17:20:12]

As mentioned on extension side, this makes more sense to me as search_criteria
rather than sink_id, but I may be misunderstanding how this is wired up.

[btolsch, 2016/03/16 18:36:30]

Done.

+  SearchProviders(string media_source, string sink_id);
 };
 
 // Interface for a service which observes state changes across media
 // sources, sinks, and issues.
 interface MediaRouter {
 
   // Represents overall media sink availability states.
   // UNAVAILABLE - No sinks are available.
   // PER_SOURCE - Sinks are available, but are only compatible with specific
   //              media sources.
@@ skipping 21 matching lines @@
 
   // 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);
 
+  // Called when the Media Route Manager receives a new list of sinks.

[amp, 2016/03/16 17:20:12]

Also as mentioned on the extension side change, this appears to be the same call
as OnSinksReceived above (in fact the comments are exactly the same).

I haven't followed through exactly why we would need a new method, there may be
a good reason I am missing.

[btolsch, 2016/03/16 18:36:30]

As mentioned on the extension side, OnSinksReceived is doing two things
differently than OnSearchSinksReceived:

1. OnSinksReceived is tracking media sources, not search criteria (here
sink_id).
2. OnSinksReceived is expecting a complete list of sinks that are compatible
with a media source but search is only providing additional sinks.

To make this work with a single function, search would have to send a complete
sink list and something other than a media source would have to be used as the
tracking key. I don't think we can overload the string to have both key
meanings, so maybe we could add an enum that indicates which type of key we're
using? This would also let us still only send search results as additions
instead of complete lists.

+  OnSearchSinksReceived(string sink_id, array<MediaSink> sinks);
+
   // 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);
 
   // Called when the presentation connected to route |route_id| has closed.
   OnPresentationConnectionClosed(
       string route_id, PresentationConnectionCloseReason reason,
       string message);
 };