Pass a TimeTicks along video capture pipeline to represent capture time

chrome/renderer/media/cast_rtp_stream.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/media/cast_rtp_stream.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 214 matching lines @@
   }
 
   // This static method is used to forward video frames to |frame_input|.
   static void OnVideoFrame(
       // These parameters are already bound when callback is created.
       const gfx::Size& expected_coded_size,
       const CastRtpStream::ErrorCallback& error_callback,
       const scoped_refptr<media::cast::VideoFrameInput> frame_input,
       // These parameters are passed for each frame.
       const scoped_refptr<media::VideoFrame>& frame,
-      const media::VideoCaptureFormat& format) {
+      const media::VideoCaptureFormat& format,
+      const base::TimeTicks& estimated_capture_time) {
     if (frame->coded_size() != expected_coded_size) {
       error_callback.Run("Video frame resolution does not match config.");
       return;
     }
 
-    const base::TimeTicks now = base::TimeTicks::Now();
+    base::TimeTicks timestamp = base::TimeTicks::Now();

[miu, 2014/05/31 02:37:26]

nit: Avoid unnecessary probing of system clock with:

base::TimeTicks timestamp;
if (estimated_capture_time.is_null())
  timestamp = base::TimeTicks::Now();
else
  timestamp = estimated_capture_time;

+    if (!estimated_capture_time.is_null())
+      timestamp = estimated_capture_time;
 
     // Used by chrome/browser/extension/api/cast_streaming/performance_test.cc
     TRACE_EVENT_INSTANT2(
         "cast_perf_test", "MediaStreamVideoSink::OnVideoFrame",
         TRACE_EVENT_SCOPE_THREAD,
-        "timestamp",  now.ToInternalValue(),
+        "timestamp",  timestamp.ToInternalValue(),
         "time_delta", frame->timestamp().ToInternalValue());
-    frame_input->InsertRawVideoFrame(frame, now);
+    frame_input->InsertRawVideoFrame(frame, timestamp);
   }
 
   // Attach this sink to a video track represented by |track_|.
   // Data received from the track will be submitted to |frame_input|.
   void AddToTrack(
       const scoped_refptr<media::cast::VideoFrameInput>& frame_input) {
     DCHECK(!sink_added_);
     sink_added_ = true;
     AddToVideoTrack(
         this,
@@ skipping 274 matching lines @@
 }
 
 void CastRtpStream::DidEncounterError(const std::string& message) {
   // Save the WeakPtr first because the error callback might delete this object.
   base::WeakPtr<CastRtpStream> ptr = weak_factory_.GetWeakPtr();
   error_callback_.Run(message);
   content::RenderThread::Get()->GetMessageLoop()->PostTask(
       FROM_HERE,
       base::Bind(&CastRtpStream::Stop, ptr));
 }