Add new files for VideoSourceBase to roll into Chrome in preparation for implementatin.

webrtc/media/base/videosourcebase.cc

Index: webrtc/media/base/videosourcebase.cc
diff --git a/webrtc/build/no_op.cc b/webrtc/media/base/videosourcebase.cc
similarity index 70%
copy from webrtc/build/no_op.cc
copy to webrtc/media/base/videosourcebase.cc
index 7508b9dbb4a3b129157f7f639acfc3496bb37183..28088ee56da1fbd3dc55fb346502fc3df50893d6 100644
--- a/webrtc/build/no_op.cc
+++ b/webrtc/media/base/videosourcebase.cc
@@ -1,5 +1,5 @@
 /*
- *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
@@ -8,7 +8,6 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-// No-op main() to provide a dummy executable target.
-int main() {
-  return 0;
-}
+#include "webrtc/media/base/videosourcebase.h"
+
+// TODO(perkj): Add implementation.