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

content/renderer/media/webmediaplayer_impl.cc

Index: content/renderer/media/webmediaplayer_impl.cc
diff --git a/content/renderer/media/webmediaplayer_impl.cc b/content/renderer/media/webmediaplayer_impl.cc
index 9d516c92da29b3a0af13cd04e8743e569bcc6d84..2aad3ceb93f9d778bbbabbfd8dc10f8c1e8e87a4 100644
--- a/content/renderer/media/webmediaplayer_impl.cc
+++ b/content/renderer/media/webmediaplayer_impl.cc
@@ -536,9 +536,16 @@ bool WebMediaPlayerImpl::didLoadingProgress() {
   return pipeline_progress || data_progress;
 }
 
-void WebMediaPlayerImpl::paint(WebCanvas* canvas,
-                               const WebRect& rect,
+void WebMediaPlayerImpl::paint(blink::WebCanvas* canvas,
+                               const blink::WebRect& rect,
                                unsigned char alpha) {
+  paint(canvas, rect, alpha, SkXfermode::kSrcOver_Mode);
+}
+
+void WebMediaPlayerImpl::paint(blink::WebCanvas* canvas,
+                               const blink::WebRect& rect,
+                               unsigned char alpha,
+                               SkXfermode::Mode mode) {
   DCHECK(main_loop_->BelongsToCurrentThread());
   TRACE_EVENT0("media", "WebMediaPlayerImpl:paint");
 
@@ -556,6 +563,7 @@ void WebMediaPlayerImpl::paint(WebCanvas* canvas,
                                  canvas,
                                  gfx_rect,
                                  alpha,
+                                 mode,
                                  pipeline_metadata_.video_rotation);
 }