Pass a TimeTicks along video capture pipeline to represent capture time

content/common/media/video_capture.h

Index: content/common/media/video_capture.h
diff --git a/content/common/media/video_capture.h b/content/common/media/video_capture.h
index bf43ebbcda8ed39ff74a3239a983cc81e65f74b6..78bce6a9940a8ee93587e8090e150e4410f13728 100644
--- a/content/common/media/video_capture.h
+++ b/content/common/media/video_capture.h
@@ -32,9 +32,24 @@ typedef base::Callback<void(VideoCaptureState)>
     VideoCaptureStateUpdateCB;
 typedef base::Callback<void(const media::VideoCaptureFormats&)>
     VideoCaptureDeviceFormatsCB;
+

[Alpha Left Google, 2014/05/31 00:34:50]

I have moved the definition of this callback to media_stream_video_sink.h to
avoid duplicated definition.

+// This callback is used to deliver video frames.
+// |video_frame| - An object of a video frame.
+// |format| - Format and additional information such as frame rate.

[Ami GONE FROM CHROMIUM, 2014/05/19 19:01:46]

neither of these 2 lines are adding value.

[Alpha Left Google, 2014/05/31 00:34:50]

Done.

+// |start_ticks| - An optional field to provide additional timing
+// information for the beginning of this stream of video frames.

[Ami GONE FROM CHROMIUM, 2014/05/19 19:01:46]

These 2 lines would be clearer as:
The time at the start of this stream, if available.

+// This field usually means the local time when the first video frame of
+// this stream is generated. It is possible for this value to be null if

[Ami GONE FROM CHROMIUM, 2014/05/19 19:01:46]

s/stream is/stream was/

[Alpha Left Google, 2014/05/31 00:34:50]

Done.

+// this timing information cannot be determined. There is no gurantee that

[Ami GONE FROM CHROMIUM, 2014/05/19 19:01:46]

typo: gurantee

[Alpha Left Google, 2014/05/31 00:34:50]

Done.

+// this value is accurate. For example video frames from a remote source
+// can only provide this timing information as an estimation.

[Ami GONE FROM CHROMIUM, 2014/05/19 19:01:46]

estimation -> estimate

[Alpha Left Google, 2014/05/31 00:34:50]

Done.

+// This field is used for synchronization with other audio or video streams.
+// |video_frame->timestamp() + start_ticks| will give an estimation in local

[Ami GONE FROM CHROMIUM, 2014/05/19 19:01:46]

estimation -> estimate

[Alpha Left Google, 2014/05/31 00:34:50]

Done.

+// time when the frame is generated.

[Ami GONE FROM CHROMIUM, 2014/05/19 19:01:46]

s/is/was/

 typedef base::Callback<
-  void(const scoped_refptr<media::VideoFrame>&,
-       const media::VideoCaptureFormat&)>
+  void(const scoped_refptr<media::VideoFrame>& video_frame,
+       const media::VideoCaptureFormat& format,
+       const base::TimeTicks& start_ticks)>
     VideoCaptureDeliverFrameCB;
 
 }  // namespace content