Decouple capture timestamp and reference time

media/capture/video/video_capture_device.h

Index: media/capture/video/video_capture_device.h
diff --git a/media/capture/video/video_capture_device.h b/media/capture/video/video_capture_device.h
index 24dec1d185780911d032f77b4f48eedcd34dfd02..c1b6353dbc43b39079d081a84bf32993b4e91289 100644
--- a/media/capture/video/video_capture_device.h
+++ b/media/capture/video/video_capture_device.h
@@ -200,12 +200,17 @@ class MEDIA_EXPORT VideoCaptureDevice {
     // The format of the frame is described by |frame_format|, and is assumed to
     // be tightly packed. This method will try to reserve an output buffer and
     // copy from |data| into the output buffer. If no output buffer is
-    // available, the frame will be silently dropped.
+    // available, the frame will be silently dropped. |referernce_time| is

[miu, 2016/05/18 22:35:40]

typo: s/referernce_time/reference_time/

[qiangchen, 2016/05/20 17:55:14]

Done.

+    // estimated system clock time when the capture happened. |timestamp|

[miu, 2016/05/18 22:35:40]

Remove "estimated" since we really *are* taking a snapshot of system clock time.
;-)

IMO, it's also worth mentioning: "The reference time is used to achieve A/V
sync, and not meant to be used to derive an exact presentation time for
playout."

[qiangchen, 2016/05/20 17:55:14]

Done.

+    // measures the ideal time span between the first frame in the stream and
+    // the current frame; however, the time source is not necessarily the

[miu, 2016/05/18 22:35:40]

nit: End of this sentence should be: "...however, the time source is determined
by the platform's device driver and is often not the system clock."

[qiangchen, 2016/05/20 17:55:14]

Done.

+    // system clock.
     virtual void OnIncomingCapturedData(const uint8_t* data,
                                         int length,
                                         const VideoCaptureFormat& frame_format,
                                         int clockwise_rotation,
-                                        const base::TimeTicks& timestamp) = 0;
+                                        base::TimeTicks reference_time,
+                                        base::TimeDelta timestamp) = 0;
 
     // Reserve an output buffer into which contents can be captured directly.
     // The returned Buffer will always be allocated with a memory size suitable