Removed unused async_invoker_ in WebRtcVideoCapturer

webrtc/media/engine/webrtcvideocapturer.h

Index: webrtc/media/engine/webrtcvideocapturer.h
diff --git a/webrtc/media/engine/webrtcvideocapturer.h b/webrtc/media/engine/webrtcvideocapturer.h
index 1cbfa08fe073991eb02b898ae41049ebbc111ab2..6fbfcf2ca2a9da73822fc5ba5d756e91e4a6c480 100644
--- a/webrtc/media/engine/webrtcvideocapturer.h
+++ b/webrtc/media/engine/webrtcvideocapturer.h
@@ -78,8 +78,6 @@ class WebRtcVideoCapturer : public VideoCapturer,
   int captured_frames_;
   std::vector<uint8_t> capture_buffer_;
   rtc::Thread* start_thread_;  // Set in Start(), unset in Stop();
-
-  std::unique_ptr<rtc::AsyncInvoker> async_invoker_;
 };
 
 }  // namespace cricket