Fix timestamp drift in CanvasCaptureHandler

content/renderer/media/canvas_capture_handler.cc

 // Copyright 2015 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 "content/renderer/media/canvas_capture_handler.h"
 
 #include <utility>
 
 #include "base/base64.h"
 #include "base/bind_helpers.h"
@@ skipping 176 matching lines @@
                           kUnpremul_SkAlphaType);
     last_size = size;
   }
 
   if(!image->readPixels(image_info_, &temp_data_[0], row_bytes_, 0, 0)) {
     DLOG(ERROR) << "Couldn't read SkImage pixels";
     return;
   }
 
   const bool isOpaque = image->isOpaque();
+  const base::TimeTicks timestamp = base::TimeTicks::Now();
   scoped_refptr<media::VideoFrame> video_frame = frame_pool_.CreateFrame(
       isOpaque ? media::PIXEL_FORMAT_I420 : media::PIXEL_FORMAT_YV12A, size,
-      gfx::Rect(size), size, base::TimeTicks::Now() - base::TimeTicks());
+      gfx::Rect(size), size, timestamp - base::TimeTicks());
   DCHECK(video_frame);
 
   // TODO(emircan): Use https://code.google.com/p/libyuv/issues/detail?id=572
   // when it becomes available.
   libyuv::ARGBToI420(temp_data_.data(), row_bytes_,
                      video_frame->data(media::VideoFrame::kYPlane),
                      video_frame->stride(media::VideoFrame::kYPlane),
                      video_frame->data(media::VideoFrame::kUPlane),
                      video_frame->stride(media::VideoFrame::kUPlane),
                      video_frame->data(media::VideoFrame::kVPlane),
                      video_frame->stride(media::VideoFrame::kVPlane),
                      size.width(), size.height());
   if (!isOpaque) {
     for (int p = 0; p < size.GetArea(); ++p)
       video_frame->data(media::VideoFrame::kAPlane)[p] = temp_data_[p * 4 + 3];
   }
 
   io_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&CanvasCaptureHandler::CanvasCaptureHandlerDelegate::
                      SendNewFrameOnIOThread,
-                 delegate_->GetWeakPtrForIOThread(), video_frame,
-                 base::TimeTicks::Now()));
+                 delegate_->GetWeakPtrForIOThread(), video_frame, timestamp));
 }
 
 void CanvasCaptureHandler::AddVideoCapturerSourceToVideoTrack(
     scoped_ptr<media::VideoCapturerSource> source,
     blink::WebMediaStreamTrack* web_track) {
   std::string str_track_id;
   base::Base64Encode(base::RandBytesAsString(64), &str_track_id);
   const blink::WebString track_id = base::UTF8ToUTF16(str_track_id);
   blink::WebMediaStreamSource webkit_source;
   scoped_ptr<MediaStreamVideoSource> media_stream_source(
       new MediaStreamVideoCapturerSource(
           MediaStreamSource::SourceStoppedCallback(), std::move(source)));
   webkit_source.initialize(track_id, blink::WebMediaStreamSource::TypeVideo,
                            track_id, false, true);
   webkit_source.setExtraData(media_stream_source.get());
 
   web_track->initialize(webkit_source);
   blink::WebMediaConstraints constraints;
   constraints.initialize();
   web_track->setExtraData(new MediaStreamVideoTrack(
       media_stream_source.release(), constraints,
       MediaStreamVideoSource::ConstraintsCallback(), true));
 }
 
 }  // namespace content