Revert of Delete cricket::VideoFrame::GetTimeStamp.

webrtc/media/engine/webrtcvideoengine2.cc

Index: webrtc/media/engine/webrtcvideoengine2.cc
diff --git a/webrtc/media/engine/webrtcvideoengine2.cc b/webrtc/media/engine/webrtcvideoengine2.cc
index d2e44cb6815003f6d843e1b27e87a39a6fb7bdb9..2dec8f43b6c738875eabb4bb1f252608382ec9d0 100644
--- a/webrtc/media/engine/webrtcvideoengine2.cc
+++ b/webrtc/media/engine/webrtcvideoengine2.cc
@@ -1664,8 +1664,9 @@
     return;
   }
 
-  int64_t frame_delta_ms = frame.timestamp_us() / rtc::kNumMicrosecsPerMillisec;
-
+  int64_t frame_delta_ms = frame.GetTimeStamp() / rtc::kNumNanosecsPerMillisec;
+
+  // frame->GetTimeStamp() is essentially a delta, align to webrtc time
   if (!first_frame_timestamp_ms_) {
     first_frame_timestamp_ms_ =
         rtc::Optional<int64_t>(rtc::TimeMillis() - frame_delta_ms);