Use microsecond timestamp in cricket::VideoFrame.

webrtc/media/engine/webrtcvideoframe.h

Index: webrtc/media/engine/webrtcvideoframe.h
diff --git a/webrtc/media/engine/webrtcvideoframe.h b/webrtc/media/engine/webrtcvideoframe.h
index 0e1d8099bcae34b37fdfc9a658b8b2670df78b77..a2034ec77d5911e5dbeaccbd98a948de0dc67399 100644
--- a/webrtc/media/engine/webrtcvideoframe.h
+++ b/webrtc/media/engine/webrtcvideoframe.h
@@ -27,6 +27,13 @@ struct CapturedFrame;
 class WebRtcVideoFrame : public VideoFrame {
  public:
   WebRtcVideoFrame();
+
+  // Preferred construction, with microsecond timestamp.
+  WebRtcVideoFrame(const rtc::scoped_refptr<webrtc::VideoFrameBuffer>& buffer,
+                   webrtc::VideoRotation rotation,
+                   int64_t timestamp_us);
+
+  // TODO(nisse): Deprecate/delete.
   WebRtcVideoFrame(const rtc::scoped_refptr<webrtc::VideoFrameBuffer>& buffer,
                    int64_t time_stamp_ns,
                    webrtc::VideoRotation rotation);
@@ -47,8 +54,13 @@ class WebRtcVideoFrame : public VideoFrame {
             int64_t time_stamp_ns,
             webrtc::VideoRotation rotation);
 
+  // The timestamp of the captured frame is expected to use the same
+  // timescale and epoch as rtc::Time.
+  // TODO(nisse): Consider adding a warning message, or even an RTC_DCHECK, if
+  // the time is too far off.
   bool Init(const CapturedFrame* frame, int dw, int dh, bool apply_rotation);
 
+  void InitToEmptyBuffer(int w, int h);
   void InitToEmptyBuffer(int w, int h, int64_t time_stamp_ns);
 
   bool InitToBlack(int w, int h, int64_t time_stamp_ns);
@@ -69,10 +81,9 @@ class WebRtcVideoFrame : public VideoFrame {
   rtc::scoped_refptr<webrtc::VideoFrameBuffer> video_frame_buffer()
       const override;
 
-  int64_t GetTimeStamp() const override { return time_stamp_ns_; }
-  void SetTimeStamp(int64_t time_stamp_ns) override {
-    time_stamp_ns_ = time_stamp_ns;
-  }
+  /* System monotonic clock */
+  int64_t timestamp_us() const override { return timestamp_us_; }
+  void set_timestamp_us(int64_t time_us) override { timestamp_us_ = time_us; };
 
   webrtc::VideoRotation rotation() const override { return rotation_; }
 
@@ -95,15 +106,15 @@ class WebRtcVideoFrame : public VideoFrame {
   // |dh| is destination height, like |dw|, but must be a positive number.
   // Returns whether the function succeeded or failed.
   bool Reset(uint32_t format,
-                     int w,
-                     int h,
-                     int dw,
-                     int dh,
-                     uint8_t* sample,
-                     size_t sample_size,
-                     int64_t time_stamp_ns,
-                     webrtc::VideoRotation rotation,
-                     bool apply_rotation);
+             int w,
+             int h,
+             int dw,
+             int dh,
+             uint8_t* sample,
+             size_t sample_size,
+             int64_t timestamp_us,
+             webrtc::VideoRotation rotation,
+             bool apply_rotation);
 
  private:
   VideoFrame* CreateEmptyFrame(int w, int h,
@@ -111,7 +122,7 @@ class WebRtcVideoFrame : public VideoFrame {
 
   // An opaque reference counted handle that stores the pixel data.
   rtc::scoped_refptr<webrtc::VideoFrameBuffer> video_frame_buffer_;
-  int64_t time_stamp_ns_;
+  int64_t timestamp_us_;
   webrtc::VideoRotation rotation_;
 
   // This is mutable as the calculation is expensive but once calculated, it