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

content/browser/renderer_host/render_widget_host_view_browsertest.cc

 // Copyright (c) 2013 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 "base/command_line.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/path_service.h"
 #include "base/run_loop.h"
 #include "content/browser/gpu/compositor_util.h"
 #include "content/browser/gpu/gpu_data_manager_impl.h"
@@ skipping 473 matching lines @@
     if (!result) {
       quit_callback.Run();
       return;
     }
 
     media::SkCanvasVideoRenderer video_renderer;
 
     SkBitmap bitmap;
     bitmap.allocN32Pixels(video_frame->visible_rect().width(),
                           video_frame->visible_rect().height());
-    bitmap.eraseColor(SK_ColorTRANSPARENT);
+    // Don't clear the canvas because drawing a video frame by Src mode.
     SkCanvas canvas(bitmap);
-
-    video_renderer.Paint(video_frame.get(),
-                         &canvas,
-                         video_frame->visible_rect(),
-                         0xff,
-                         media::VIDEO_ROTATION_0);
+    video_renderer.Copy(video_frame.get(), &canvas);
 
     CopyFromCompositingSurfaceCallback(quit_callback,
                                        result,
                                        bitmap);
   }
 
   void SetExpectedCopyFromCompositingSurfaceResult(bool result,
                                                    const SkBitmap& bitmap) {
     expected_copy_from_compositing_surface_result_ = result;
     expected_copy_from_compositing_surface_bitmap_ = bitmap;
@@ skipping 343 matching lines @@
                         CompositingRenderWidgetHostViewBrowserTestTabCapture,
                         testing::ValuesIn(kAllCompositingModes));
 INSTANTIATE_TEST_CASE_P(GLAndSoftwareCompositing,
                         CompositingRenderWidgetHostViewTabCaptureHighDPI,
                         testing::ValuesIn(kAllCompositingModes));
 
 #endif  // !defined(OS_ANDROID) && !defined(OS_IOS)
 
 }  // namespace
 }  // namespace content