Stop IncomingVideoStream on delete.

Fixes race between VideoReceiveStream destruction and pending
IncomingVideoStream frames.

BUG=
TBR=mflodman@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/45259004

Cr-Commit-Position: refs/heads/master@{#9084}
diff --git a/webrtc/video/video_receive_stream.cc b/webrtc/video/video_receive_stream.cc
index bcb42c6..344577a 100644
--- a/webrtc/video/video_receive_stream.cc
+++ b/webrtc/video/video_receive_stream.cc
@@ -263,6 +263,7 @@
 }
 
 VideoReceiveStream::~VideoReceiveStream() {
+  incoming_video_stream_->Stop();
   vie_channel_->RegisterPreRenderCallback(nullptr);
   vie_channel_->RegisterPreDecodeImageCallback(nullptr);