[Media Router] Implement stopListeningForRouteMessages.

NOTE: This continues from https://codereview.chromium.org/1298163003/
since I wanted to upload this patch using my @chromium.org acct.

stopListeningForRouteMessages for media_router.mojom serves to resolve
the outstanding Mojo callback for a given listenForRouteMessages call.
When the call is received, the outstanding callback/promise will be
resolved with an empty list.

We also change the semantics of return value of listenForRouteMessages
to return an additional bool to indicate whether a permanent error
occurred. In cases where |error| is true, MRMojoImpl will stop asking
for next batch of msgs for that route.

Note: this patch should be landed around the same time as the patch
that implements stopListeningForRouteMessages in extension.

BUG=520204

Review URL: https://codereview.chromium.org/1307723002

Cr-Commit-Position: refs/heads/master@{#344703}

1 files changed, 23 insertions, 5 deletions

diff --git a/extensions/renderer/resources/media_router_bindings.js b/extensions/renderer/resources/media_router_bindings.js
index 6c711fd..6491d88 100644
--- a/extensions/renderer/resources/media_router_bindings.js
+++ b/extensions/renderer/resources/media_router_bindings.js
@@ -321,11 +321,17 @@ define('media_router_bindings', [
     this.sendRouteBinaryMessage = null;
 
     /**
-     * @type {function(string): Promise.<Array.<RouteMessage>>}
+     * @type {function(string):
+     *     Promise.<{messages: Array.<RouteMessage>, error: boolean}>}
      */
     this.listenForRouteMessages = null;
 
     /**
+     * @type {function(string)}
+     */
+    this.stopListeningForRouteMessages = null;
+
+    /**
      * @type {function()}
      */
     this.startObservingMediaRoutes = null;
@@ -375,6 +381,7 @@ define('media_router_bindings', [
       'sendRouteMessage',
       'sendRouteBinaryMessage',
       'listenForRouteMessages',
+      'stopListeningForRouteMessages',
       'closeRoute',
       'joinRoute',
       'createRoute',
@@ -504,19 +511,30 @@ define('media_router_bindings', [
   /**
    * Listen for next batch of messages from one of the routeIds.
    * @param {!string} routeId
-   * @return {!Promise.<Array.<RouteMessage>>} Resolved with a list of messages,
-   *    an empty list if an error occurred.
+   * @return {!Promise.<{messages: Array.<RouteMessage>, error: boolean}>}
+   *     Resolved with a list of messages, and a boolean indicating if an error
+   *     occurred.
    */
   MediaRouteProvider.prototype.listenForRouteMessages = function(routeId) {
     return this.handlers_.listenForRouteMessages(routeId)
         .then(function(messages) {
-          return {'messages': messages.map(messageToMojo_)};
+          return {'messages': messages.map(messageToMojo_), 'error': false};
         }, function() {
-          return {'messages': []};
+          return {'messages': [], 'error': true};
         });
   };
 
   /**
+   * If there is an outstanding |listenForRouteMessages| promise for
+   * |routeId|, resolve that promise with an empty array.
+   * @param {!string} routeId
+   */
+  MediaRouteProvider.prototype.stopListeningForRouteMessages = function(
+      routeId) {
+    return this.handlers_.stopListeningForRouteMessages(routeId);
+  };
+
+  /**
    * Requests that the provider manager start sending information about active
    * media routes to the Media Router.
    */