Add histogram WebRTC.UserMediaRequest.NoResultState to track user media requests with no result.

content/renderer/media/media_stream_impl.h

Index: content/renderer/media/media_stream_impl.h
diff --git a/content/renderer/media/media_stream_impl.h b/content/renderer/media/media_stream_impl.h
index 0effc2a9074863c3dc6764625a4d2839a3332a31..ed37105dcf2536f991414625657a3bfde85bc24b 100644
--- a/content/renderer/media/media_stream_impl.h
+++ b/content/renderer/media/media_stream_impl.h
@@ -146,7 +146,8 @@ class CONTENT_EXPORT MediaStreamImpl
     bool IsSourceUsed(const blink::WebMediaStreamSource& source) const;
     void RemoveSource(const blink::WebMediaStreamSource& source);
 
-    bool AreAllSourcesRemoved() const { return sources_.empty(); }
+    bool AreAllSourcesRemoved() const;
+    bool HasPendingSources() const;
 
    private:
     void OnTrackStarted(MediaStreamSource* source, bool success);
@@ -191,10 +192,15 @@ class CONTENT_EXPORT MediaStreamImpl
       UserMediaRequestInfo* request,
       content::MediaStreamRequestResult result);
 
+  void OnStreamGeneratedForCancelledRequest(
+      const StreamDeviceInfoArray& audio_array,
+      const StreamDeviceInfoArray& video_array);
+
   UserMediaRequestInfo* FindUserMediaRequestInfo(int request_id);
   UserMediaRequestInfo* FindUserMediaRequestInfo(
       const blink::WebUserMediaRequest& request);
   void DeleteUserMediaRequestInfo(UserMediaRequestInfo* request);
+  void DeleteAllUserMediaRequests();
 
   MediaDevicesRequestInfo* FindMediaDevicesRequestInfo(int request_id);
   MediaDevicesRequestInfo* FindMediaDevicesRequestInfo(