Factor out authorization from AudioRendererHost.

content/browser/renderer_host/media/media_stream_manager.h

Index: content/browser/renderer_host/media/media_stream_manager.h
diff --git a/content/browser/renderer_host/media/media_stream_manager.h b/content/browser/renderer_host/media/media_stream_manager.h
index c448eafbf606d5cc7db502f3681dcc775c0fa424..420fd12cd07f8e7c9ac292ad543cdbad43cc6a57 100644
--- a/content/browser/renderer_host/media/media_stream_manager.h
+++ b/content/browser/renderer_host/media/media_stream_manager.h
@@ -252,6 +252,8 @@ class CONTENT_EXPORT MediaStreamManager
                                          const std::string& device_guid,
                                          const std::string& raw_unique_id);
 
+  static bool IsValidDeviceId(const std::string& device_id);
+
   // Returns true if the renderer process identified with |render_process_id|
   // is allowed to access |origin|.
   static bool IsOriginAllowed(int render_process_id, const url::Origin& origin);