Detect change on the intersection of video and viewport.

media/blink/webmediaplayer_impl.cc

Index: media/blink/webmediaplayer_impl.cc
diff --git a/media/blink/webmediaplayer_impl.cc b/media/blink/webmediaplayer_impl.cc
index cd6091ddd3ccfcfc26d03a634d700428c75ac598..578f7ede2799893f4ea63ba1b0b3006fefdff25e 100644
--- a/media/blink/webmediaplayer_impl.cc
+++ b/media/blink/webmediaplayer_impl.cc
@@ -365,6 +365,11 @@ void WebMediaPlayerImpl::exitedFullscreen() {
     observer_->OnExitedFullscreen();
 }
 
+void WebMediaPlayerImpl::becameDominantVisibleContent(bool isDominant) {
+  if (observer_)
+    observer_->OnBecameDominantVisibleContent(isDominant);
+}
+
 void WebMediaPlayerImpl::DoLoad(LoadType load_type,
                                 const blink::WebURL& url,
                                 CORSMode cors_mode) {