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 2787d776cafe87171a3e945114a048130349aae4..a1cecf8718b818c9c08e2977fa330904df167e6e 100644
--- a/content/renderer/media/webmediaplayer_impl.cc
+++ b/content/renderer/media/webmediaplayer_impl.cc
@@ -531,9 +531,16 @@ 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");
 
@@ -551,6 +558,7 @@ void WebMediaPlayerImpl::paint(WebCanvas* canvas,
                                  canvas,
                                  gfx_rect,
                                  alpha,
+                                 mode,
                                  pipeline_metadata_.video_rotation);
 }