Move videosinkinterface.h to common_video to solve a circular dep.

I updated some dependency enforcement rules to allow examples and pc
to depend on common_video. I reckoned depending on common_video is
not controversial when they already dependend on media/base, which
is a lower-level abstraction.

Bug: webrtc:6828
Change-Id: I77dbeb10187b4e70dda1d873a29994fa76070758
Reviewed-on: https://webrtc-review.googlesource.com/34187
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Commit-Queue: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21495}
diff --git a/api/videosinkinterface.h b/api/videosinkinterface.h
new file mode 100644
index 0000000..2399320
--- /dev/null
+++ b/api/videosinkinterface.h
@@ -0,0 +1,32 @@
+/*
+ *  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
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef API_VIDEOSINKINTERFACE_H_
+#define API_VIDEOSINKINTERFACE_H_
+
+#include <rtc_base/checks.h>
+
+namespace rtc {
+
+template <typename VideoFrameT>
+class VideoSinkInterface {
+ public:
+  virtual ~VideoSinkInterface() {}
+
+  virtual void OnFrame(const VideoFrameT& frame) = 0;
+
+  // Should be called by the source when it discards the frame due to rate
+  // limiting.
+  virtual void OnDiscardedFrame() {}
+};
+
+}  // namespace rtc
+
+#endif  // API_VIDEOSINKINTERFACE_H_