Reland of Use mojo support for Blink devicechange event.

content/renderer/media/user_media_client_impl.h

Index: content/renderer/media/user_media_client_impl.h
diff --git a/content/renderer/media/user_media_client_impl.h b/content/renderer/media/user_media_client_impl.h
index 22ddb69bea04d6d191f0c493440f0c34af8ae320..6931e7b69589e295f47011aeb0f425123e26832c 100644
--- a/content/renderer/media/user_media_client_impl.h
+++ b/content/renderer/media/user_media_client_impl.h
@@ -19,6 +19,7 @@
 #include "content/common/media/media_devices.h"
 #include "content/common/media/media_devices.mojom.h"
 #include "content/public/renderer/render_frame_observer.h"
+#include "content/renderer/media/media_devices_event_dispatcher.h"
 #include "content/renderer/media/media_stream_dispatcher_eventhandler.h"
 #include "content/renderer/media/media_stream_source.h"
 #include "services/service_manager/public/cpp/interface_provider.h"
@@ -224,7 +225,7 @@
       const StreamDeviceInfoArray& audio_array,
       const StreamDeviceInfoArray& video_array);
 
-  using EnumerationResult = std::vector<std::vector<MediaDeviceInfo>>;
+  using EnumerationResult = std::vector<MediaDeviceInfoArray>;
   void FinalizeEnumerateDevices(blink::WebMediaDevicesRequest request,
                                 const EnumerationResult& result);
 
@@ -243,6 +244,11 @@
                        bool notify_dispatcher);
 
   const ::mojom::MediaDevicesDispatcherHostPtr& GetMediaDevicesDispatcher();
+
+  // Callback invoked by MediaDevicesEventDispatcher when a device-change
+  // notification arrives.
+  void DevicesChanged(MediaDeviceType device_type,
+                      const MediaDeviceInfoArray& device_infos);
 
   // Weak ref to a PeerConnectionDependencyFactory, owned by the RenderThread.
   // It's valid for the lifetime of RenderThread.
@@ -259,6 +265,8 @@
   LocalStreamSources local_sources_;
 
   UserMediaRequests user_media_requests_;
+  MediaDevicesEventDispatcher::SubscriptionIdList
+      device_change_subscription_ids_;
 
   blink::WebMediaDeviceChangeObserver media_device_change_observer_;