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 32d5a896e44b37814eeb5ad2fc33cdfc523e9075..3cc922806eb21f4eadc6bfb9e61209702261e0f1 100644
--- a/media/blink/webmediaplayer_impl.cc
+++ b/media/blink/webmediaplayer_impl.cc
@@ -361,6 +361,11 @@ void WebMediaPlayerImpl::exitedFullscreen() {
     observer_->OnExitedFullscreen();
 }
 
+void WebMediaPlayerImpl::stablyFilledViewport(bool isMostlyFillingViewport) {
+  if (observer_)
+    observer_->OnStablyFilledViewportChanged(isMostlyFillingViewport);
+}
+
 void WebMediaPlayerImpl::DoLoad(LoadType load_type,
                                 const blink::WebURL& url,
                                 CORSMode cors_mode) {