Begin adding support for tab mirroring via the MediaStream audio/video capturing

content/browser/renderer_host/media/media_stream_dispatcher_host.h

Index: content/browser/renderer_host/media/media_stream_dispatcher_host.h
diff --git a/content/browser/renderer_host/media/media_stream_dispatcher_host.h b/content/browser/renderer_host/media/media_stream_dispatcher_host.h
index 0c664bda1c4f1ba970ae1df75c42dc7cd374f811..4f46abf943b83c0aa6c411844987c0279b1ccb30 100644
--- a/content/browser/renderer_host/media/media_stream_dispatcher_host.h
+++ b/content/browser/renderer_host/media/media_stream_dispatcher_host.h
@@ -54,6 +54,11 @@ class CONTENT_EXPORT MediaStreamDispatcherHost
                         int page_request_id,
                         const StreamOptions& components,
                         const GURL& security_origin);
+  void OnGenerateStreamForDevice(int render_view_id,
+                                 int page_request_id,
+                                 const StreamOptions& components,
+                                 const std::string& device_id,
+                                 const GURL& security_origin);
   void OnCancelGenerateStream(int render_view_id,
                               int page_request_id);
   void OnStopGeneratedStream(int render_view_id, const std::string& label);