Reland of 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/api/video/video_content_type.h b/webrtc/api/video/video_content_type.h
new file mode 100644
index 0000000000000000000000000000000000000000..5c468c079d35ea2d20c115234cf38d7e7fcd42bd
--- /dev/null
+++ b/webrtc/api/video/video_content_type.h
@@ -0,0 +1,26 @@
+/*
+ *  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
+ *  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 WEBRTC_API_VIDEO_VIDEO_CONTENT_TYPE_H_
+#define WEBRTC_API_VIDEO_VIDEO_CONTENT_TYPE_H_
+
+#include <stdint.h>
+
+namespace webrtc {
+
+enum class VideoContentType : uint8_t {
+  UNSPECIFIED = 0,
+  SCREENSHARE = 1,
+  TOTAL_CONTENT_TYPES  // Must be the last value in the enum.
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_API_VIDEO_VIDEO_CONTENT_TYPE_H_