Build WebRTC with data channel only.

webrtc/api/mediastreaminterface.h

Index: webrtc/api/mediastreaminterface.h
diff --git a/webrtc/api/mediastreaminterface.h b/webrtc/api/mediastreaminterface.h
index 2acaa000e4898ca1f2c067d1b605b5561d42d406..937bb67ae91ddc85c03093462d4d9cb320595940 100644
--- a/webrtc/api/mediastreaminterface.h
+++ b/webrtc/api/mediastreaminterface.h
@@ -23,10 +23,16 @@
 #include <vector>
 
 #include "webrtc/api/video/video_frame.h"
+#include "webrtc/base/optional.h"
+// TODO(zhihuang): Remove unrelated headers once downstream applications stop
+// relying on them; they were previously transitively included by
+// mediachannel.h, which is no longer a dependency of this file.
+#include "webrtc/base/ratetracker.h"
 #include "webrtc/base/refcount.h"
 #include "webrtc/base/scoped_ref_ptr.h"
-#include "webrtc/base/optional.h"
-#include "webrtc/media/base/mediachannel.h"
+#include "webrtc/base/thread.h"
+#include "webrtc/base/timeutils.h"
+#include "webrtc/media/base/streamparams.h"
 #include "webrtc/media/base/videosinkinterface.h"
 #include "webrtc/media/base/videosourceinterface.h"