Add cricket::VideoFrame::frame_id() and set it to RTP timestamp.

webrtc/media/engine/webrtcvideoframe.cc

Index: webrtc/media/engine/webrtcvideoframe.cc
diff --git a/webrtc/media/engine/webrtcvideoframe.cc b/webrtc/media/engine/webrtcvideoframe.cc
index 4f89c8b85d100562d14cb891c6b11e8f67f247d1..0bedca4eaf15fb2ad2f77656c5666f401a0d6643 100644
--- a/webrtc/media/engine/webrtcvideoframe.cc
+++ b/webrtc/media/engine/webrtcvideoframe.cc
@@ -28,9 +28,11 @@ WebRtcVideoFrame::WebRtcVideoFrame()
 WebRtcVideoFrame::WebRtcVideoFrame(
     const rtc::scoped_refptr<webrtc::VideoFrameBuffer>& buffer,
     webrtc::VideoRotation rotation,
-    int64_t timestamp_us)
+    int64_t timestamp_us,
+    uint32_t frame_id)
     : video_frame_buffer_(buffer),
       timestamp_us_(timestamp_us),
+      frame_id_(frame_id),
       rotation_(rotation) {}
 
 WebRtcVideoFrame::WebRtcVideoFrame(
@@ -39,7 +41,8 @@ WebRtcVideoFrame::WebRtcVideoFrame(
     webrtc::VideoRotation rotation)
     : WebRtcVideoFrame(buffer,
                        rotation,
-                       time_stamp_ns / rtc::kNumNanosecsPerMicrosec) {}
+                       time_stamp_ns / rtc::kNumNanosecsPerMicrosec,
+                       0) {}
 
 WebRtcVideoFrame::~WebRtcVideoFrame() {}
 
@@ -78,8 +81,25 @@ WebRtcVideoFrame::video_frame_buffer() const {
   return video_frame_buffer_;
 }
 
+uint32_t WebRtcVideoFrame::frame_id() const {
+  return frame_id_;
+}
+
+int64_t WebRtcVideoFrame::timestamp_us() const {
+  return timestamp_us_;
+}
+
+void WebRtcVideoFrame::set_timestamp_us(int64_t time_us) {
+  timestamp_us_ = time_us;
+}
+
+webrtc::VideoRotation WebRtcVideoFrame::rotation() const {
+  return rotation_;
+}
+
 VideoFrame* WebRtcVideoFrame::Copy() const {
-  return new WebRtcVideoFrame(video_frame_buffer_, rotation_, timestamp_us_);
+  return new WebRtcVideoFrame(video_frame_buffer_, rotation_, timestamp_us_,
+                              frame_id_);
 }
 
 size_t WebRtcVideoFrame::ConvertToRgbBuffer(uint32_t to_fourcc,