Implement timing frames.

webrtc/test/frame_generator_capturer.cc

Index: webrtc/test/frame_generator_capturer.cc
diff --git a/webrtc/test/frame_generator_capturer.cc b/webrtc/test/frame_generator_capturer.cc
index bd3f8ca2a0839371df981313b854df182cfc9e8e..c114e0e098a591216e6d44741f6a165180317c1c 100644
--- a/webrtc/test/frame_generator_capturer.cc
+++ b/webrtc/test/frame_generator_capturer.cc
@@ -160,7 +160,7 @@ void FrameGeneratorCapturer::InsertFrame() {
   rtc::CritScope cs(&lock_);
   if (sending_) {
     VideoFrame* frame = frame_generator_->NextFrame();
-    frame->set_timestamp_us(rtc::TimeMicros());
+    frame->set_timestamp_us(clock_->TimeInMicroseconds());

[ilnik, 2017/06/01 12:33:37]

For consistency.

[nisse-webrtc, 2017/06/02 12:04:55]

I'd rather move in the opposite direction. The frame timestamp_us should always
be in rtc::TimeMicros timescale (see comments in api/video/video_frame.h).

Not sure what's the best way to get ntp time (on the line below) without using
webrtc::Clock. timeutils.h declares a function TimeUTCMicros, which has a
compile-time constant offset to ntp time.

[ilnik, 2017/06/02 13:02:21]

I believe we should use clock_ instead of wallclock time if available. What if
we are inside some kind of test? Also, in case of realtime clock_, at least on
linux, it boils down to rtc:TimeMicros().

[sprang_webrtc, 2017/06/09 11:02:01]

Agree that we should move towards rtc::TimeMicros rather than Clock, but then we
should do so for the whole file at once, just so we're not using a fake clock
for some of the calls but not others... This CL is already very large, I think
that refactoring can "wait" for a follow-up.

     frame->set_ntp_time_ms(clock_->CurrentNtpInMilliseconds());
     frame->set_rotation(fake_rotation_);
     if (first_frame_capture_time_ == -1) {