Fix NullVideoEngine's CreateChannel implementation.

BUG=
R=pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/44149004

Cr-Commit-Position: refs/heads/master@{#8980}
diff --git a/talk/media/base/mediaengine.h b/talk/media/base/mediaengine.h
index 61424d2..8186ad1 100644
--- a/talk/media/base/mediaengine.h
+++ b/talk/media/base/mediaengine.h
@@ -336,6 +336,7 @@
   int GetCapabilities() { return 0; }
   // If you need this to return an actual channel, use FakeMediaEngine instead.
   VideoMediaChannel* CreateChannel(
+      const VideoOptions& options,
       VoiceMediaChannel* voice_media_channel) {
     return NULL;
   }