[Media Router] Implement JoinRoute + update CreateRoute API.

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 {
   // The sink identifier, e.g. "rs71w7mFzYLFlabir_qO4NHl6SUc."
   string sink_id;
@@ skipping 66 matching lines @@
   array<ActionType>? secondary_actions;
 
   // A help page to be opened if users select learn_more.
   string? help_url;
 };
 
 // Modeled after the MediaRouter interface defined in
 // chrome/browser/media/router/media_router.h
 interface MediaRouter {
   // Initiates a media route from |media_source| to |sink_id|.
+  // The presentation ID of the route created will be |presentation_id|, but it
+  // may be overridden by a provider implementation. The presentation ID will

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

Does any provider actually do this?  Last time I checked the Cast MRP did not
need to override the id for new routes.

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

I remember in the Start + Join doc that there was a use case where presentation
ID was overridden by the Cast MRP?

+  // be used by the presentation API to refer to the created route.
+  // |origin| and |tab_id| may be passed in for enforcing same-origin and/or
+  // same-tab scopes and are optional.
+  // Since int types cannot be made optional, use -1 as |tab_id| in cases where
+  // it is not applicable.
   // If the operation was successful, |route| will be defined and
   //     |error_text| will be null.
   // If the operation failed, |route| will be null and |error_text|
   //     will be set.
-  CreateRoute(string media_source, string sink_id) =>
-      (MediaRoute? route, string? error_text);
+  CreateRoute(string media_source,
+              string sink_id,
+              string presentation_id,

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

This might be better named default_presentation_id or original_presentation_id.

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

Done.

+              string? origin,
+              int32 tab_id) => (MediaRoute? route, string? error_text);
+
+  // Joins an established route given by |presentation_id|
+  // with |media_source|.
+  // |origin| and |tab_id| are used for validating same-origin/tab scopes and
+  // are optional. (See CreateRoute for additional documentation)
+  // If the operation was successful, |route| will be defined and
+  //     |error_text| will be null.
+  // If the operation failed, |route| will be null and |error_text|
+  //     will be set.
+  JoinRoute(string media_source,
+            string presentation_id,
+            string? origin,
+            int32 tab_id) => (MediaRoute? route, string? error_text);
 
   // Closes the route specified by |route_id|.
   CloseRoute(string route_id);
 
   // Sends |message| with optional |extra_info_json| via the media route
   // |media_route_id|.
   PostMessage(string media_route_id, string message);
 
   // Starts querying for sinks capable of displaying |media_source|.
   StartObservingMediaSinks(string media_source);
@@ skipping 29 matching lines @@
   // Called when the Media Route Manager receives a route message.
   OnMessage(string media_source, string message);
 
   // Called when issues are reported for media routes.
   OnIssue(Issue issue);
 
   // Called when list of routes has been updated.
   OnRoutesUpdated(array<MediaRoute> routes);
 };