Make cricket::VideoCapturer implement VideoSourceInterface

talk/media/base/fakemediaengine.h

Index: talk/media/base/fakemediaengine.h
diff --git a/talk/media/base/fakemediaengine.h b/talk/media/base/fakemediaengine.h
index c17ab28b1bd18e0cdf52ac1b3b24ad6af577ed61..f48cd41881d3b7afb2e43e96522ab5ec7dcc2eaf 100644
--- a/talk/media/base/fakemediaengine.h
+++ b/talk/media/base/fakemediaengine.h
@@ -524,6 +524,9 @@ class FakeVideoMediaChannel : public RtpHelper<VideoMediaChannel> {
     }
     return true;
   }
+  virtual rtc::VideoSinkInterface<cricket::VideoFrame>* GetSink(uint32_t ssrc) {
+    return NULL;
+  }
   virtual bool SetCapturer(uint32_t ssrc, VideoCapturer* capturer) {
     capturers_[ssrc] = capturer;
     return true;