Allow the cast tray to function as expected when the installed extension is missing API methods.

ash/cast_config_delegate.h

 // 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.
 
 #ifndef ASH_CAST_CONFIG_DELEGATE_H_
 #define ASH_CAST_CONFIG_DELEGATE_H_
 
 #include <map>
 #include <string>
 
@@ skipping 65 matching lines @@
   // Fetches the current set of receivers and their possible activities. This
   // method will lookup the current chromecast extension and query its current
   // state. The |callback| will be invoked when the receiver/activity data is
   // available.
   virtual void GetReceiversAndActivities(
       const ReceiversAndActivitesCallback& callback) = 0;
 
   // Cast to a receiver specified by |receiver_id|.
   virtual void CastToReceiver(const std::string& receiver_id) = 0;
 
-  // Stop ongoing cast. The |activity_id| is the unique identifier associated
-  // with the ongoing cast. Each receiver has only one possible activity
-  // associated with it. The |activity_id| is available by invoking
-  // GetReceiversAndActivities(); if the receiver is currently casting, then the
-  // associated activity data will have an id. This id can be used to stop the
-  // cast in this method.
-  virtual void StopCasting(const std::string& activity_id) = 0;
+  // Stop an ongoing cast.
+  virtual void StopCasting() = 0;
 
   // Opens Options page for cast.
   virtual void LaunchCastOptions() = 0;
 
  private:
   DISALLOW_ASSIGN(CastConfigDelegate);
 };
 
 }  // namespace ash
 
 #endif  // ASH_CAST_CONFIG_DELEGATE_H_