Tab Capture: Backing store readbacks to YV12 VideoFrames.

media/video/capture/mac/video_capture_device_qtkit_mac.mm

 // Copyright (c) 2012 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.
 
 #import "media/video/capture/mac/video_capture_device_qtkit_mac.h"
 
 #import <QTKit/QTKit.h>
 
 #include "base/debug/crash_logging.h"
 #include "base/logging.h"
@@ skipping 205 matching lines @@
       == kCVReturnSuccess) {
     void *baseAddress = CVPixelBufferGetBaseAddress(videoFrame);
     size_t bytesPerRow = CVPixelBufferGetBytesPerRow(videoFrame);
     int frameHeight = CVPixelBufferGetHeight(videoFrame);
     int frameSize = bytesPerRow * frameHeight;
 
     // TODO(shess): bytesPerRow may not correspond to frameWidth_*4,
     // but VideoCaptureController::OnIncomingCapturedFrame() requires
     // it to do so.  Plumbing things through is intrusive, for now
     // just deliver an adjusted buffer.
+    // TODO(nick): This workaround could probably be eliminated by using
+    // VideoCaptureController::OnIncomingCapturedVideoFrame, which supports
+    // pitches.
     UInt8* addressToPass = static_cast<UInt8*>(baseAddress);
     size_t expectedBytesPerRow = frameWidth_ * 4;
     if (bytesPerRow > expectedBytesPerRow) {
       // TODO(shess): frameHeight and frameHeight_ are not the same,
       // try to do what the surrounding code seems to assume.
       // Ironically, captureCapability and frameSize are ignored
       // anyhow.
       adjustedFrame_.resize(expectedBytesPerRow * frameHeight);
       // std::vector is contiguous according to standard.
       UInt8* adjustedAddress = &adjustedFrame_[0];
@@ skipping 17 matching lines @@
 
     // Deliver the captured video frame.
     frameReceiver_->ReceiveFrame(addressToPass, frameSize, captureCapability);
 
     CVPixelBufferUnlockBaseAddress(videoFrame, kLockFlags);
   }
   [lock_ unlock];
 }
 
 @end