Add content type information to encoded images and corresponding rtp extension header

webrtc/api/video/video_content_type.h

Index: webrtc/api/video/video_content_type.h
diff --git a/webrtc/test/constants.h b/webrtc/api/video/video_content_type.h
similarity index 58%
copy from webrtc/test/constants.h
copy to webrtc/api/video/video_content_type.h
index 1b5b0cb1050089ce062232b4ce597408856513f4..8091fbaf2a1dc23356ca1522c52545c6d073d1a6 100644
--- a/webrtc/test/constants.h
+++ b/webrtc/api/video/video_content_type.h
@@ -1,5 +1,5 @@
 /*
- *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
+ *  Copyright (c) 2017 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
@@ -8,12 +8,16 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#ifndef WEBRTC_API_VIDEO_VIDEO_CONTENT_TYPE_H_
+#define WEBRTC_API_VIDEO_VIDEO_CONTENT_TYPE_H_
+
 namespace webrtc {
-namespace test {
 
-extern const int kTOffsetExtensionId;
-extern const int kAbsSendTimeExtensionId;
-extern const int kTransportSequenceNumberExtensionId;
-extern const int kVideoRotationExtensionId;
-}  // namespace test
+enum class VideoContentType {
+  kDefault = 0,
+  kScreenshare = 1,
+};
+
 }  // namespace webrtc
+
+#endif  // WEBRTC_API_VIDEO_VIDEO_CONTENT_TYPE_H_