2D Canvas doesn't blend video with the destination buffer.

media/filters/skcanvas_video_renderer.cc

 // 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.
 
 #include "media/filters/skcanvas_video_renderer.h"
 
 #include "base/logging.h"
 #include "media/base/video_frame.h"
 #include "media/base/yuv_convert.h"
 #include "third_party/libyuv/include/libyuv.h"
@@ skipping 170 matching lines @@
 
 SkCanvasVideoRenderer::SkCanvasVideoRenderer()
     : last_frame_timestamp_(media::kNoTimestamp()) {
 }
 
 SkCanvasVideoRenderer::~SkCanvasVideoRenderer() {}
 
 void SkCanvasVideoRenderer::Paint(media::VideoFrame* video_frame,
                                   SkCanvas* canvas,
                                   const gfx::RectF& dest_rect,
-                                  uint8 alpha) {
+                                  uint8 alpha,
+                                  SkXfermode::Mode mode) {
   if (alpha == 0) {
     return;
   }
 
   SkRect dest;
   dest.set(dest_rect.x(), dest_rect.y(), dest_rect.right(), dest_rect.bottom());
 
   SkPaint paint;
   paint.setAlpha(alpha);
 
   // Paint black rectangle if there isn't a frame available or the
   // frame has an unexpected format.
   if (!video_frame || !IsYUVOrNative(video_frame->format())) {
     canvas->drawRect(dest, paint);
     return;
   }
 
   // Check if we should convert and update |last_frame_|.
   if (last_frame_.isNull() ||
       video_frame->timestamp() != last_frame_timestamp_) {
     ConvertVideoFrameToBitmap(video_frame, &last_frame_);
     last_frame_timestamp_ = video_frame->timestamp();
   }
 
-  // Use SRC mode so we completely overwrite the buffer (in case we have alpha)
-  // this means we don't need the extra cost of clearing the buffer first.
-  paint.setXfermode(SkXfermode::Create(SkXfermode::kSrc_Mode));
+  paint.setXfermodeMode(mode);
 
   // Paint using |last_frame_|.
   paint.setFilterLevel(SkPaint::kLow_FilterLevel);
   canvas->drawBitmapRect(last_frame_, NULL, dest, &paint);
 }
 
 }  // namespace media