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

content/renderer/media/webmediaplayer_ms.cc

Index: content/renderer/media/webmediaplayer_ms.cc
diff --git a/content/renderer/media/webmediaplayer_ms.cc b/content/renderer/media/webmediaplayer_ms.cc
index b466d3168aab617b38a6ea1dde0b46a2e174ceeb..e980e0b8b0115eae03f148f61a1e44aa5f14cfb7 100644
--- a/content/renderer/media/webmediaplayer_ms.cc
+++ b/content/renderer/media/webmediaplayer_ms.cc
@@ -316,14 +316,25 @@ bool WebMediaPlayerMS::didLoadingProgress() {
   return true;
 }
 
-void WebMediaPlayerMS::paint(WebCanvas* canvas,
-                             const WebRect& rect,
+void WebMediaPlayerMS::paint(blink::WebCanvas* canvas,
+                             const blink::WebRect& rect,
                              unsigned char alpha) {
+  paint(canvas, rect, alpha, SkXfermode::kSrcOver_Mode);
+}
+
+void WebMediaPlayerMS::paint(blink::WebCanvas* canvas,
+                             const blink::WebRect& rect,
+                             unsigned char alpha,
+                             SkXfermode::Mode mode) {
   DVLOG(3) << "WebMediaPlayerMS::paint";
   DCHECK(thread_checker_.CalledOnValidThread());
 
   gfx::RectF dest_rect(rect.x, rect.y, rect.width, rect.height);
-  video_renderer_.Paint(current_frame_.get(), canvas, dest_rect, alpha);
+  video_renderer_.Paint(current_frame_.get(),
+                        canvas,
+                        dest_rect,
+                        alpha,
+                        mode);
 
   {
     base::AutoLock auto_lock(current_frame_lock_);