Revert of Remove MediaStreamTrack.getSources().

third_party/WebKit/Source/modules/mediastream/UserMediaClient.h

Index: third_party/WebKit/Source/modules/mediastream/UserMediaClient.h
diff --git a/third_party/WebKit/Source/modules/mediastream/UserMediaClient.h b/third_party/WebKit/Source/modules/mediastream/UserMediaClient.h
index 70b8fe1d7837515d458b4b7cf239708b02775226..43e5f19c3b694865b3b9ac7533efb90e1869b891 100644
--- a/third_party/WebKit/Source/modules/mediastream/UserMediaClient.h
+++ b/third_party/WebKit/Source/modules/mediastream/UserMediaClient.h
@@ -34,6 +34,7 @@
 #include "modules/ModulesExport.h"
 #include "modules/mediastream/MediaDevicesRequest.h"
 #include "modules/mediastream/UserMediaRequest.h"
+#include "platform/mediastream/MediaStreamTrackSourcesRequest.h"
 #include "wtf/Allocator.h"
 
 namespace blink {
@@ -48,6 +49,7 @@
   virtual void requestUserMedia(UserMediaRequest*) = 0;
   virtual void cancelUserMediaRequest(UserMediaRequest*) = 0;
   virtual void requestMediaDevices(MediaDevicesRequest*) = 0;
+  virtual void requestSources(MediaStreamTrackSourcesRequest*) = 0;
   virtual void setMediaDeviceChangeObserver(MediaDevices*) = 0;
   virtual ~UserMediaClient() {}
 };