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..ef45447cde8160c6538752b9e54edc0db072214c 100644
--- a/media/blink/webmediaplayer_impl.cc
+++ b/media/blink/webmediaplayer_impl.cc
@@ -361,6 +361,12 @@ void WebMediaPlayerImpl::exitedFullscreen() {
     observer_->OnExitedFullscreen();
 }
 
+void WebMediaPlayerImpl::stablyFilledMostViewport(
+    bool isMostlyFillingViewport) {
+  if (observer_)
+    observer_->OnStablyFilledMostViewportChanged(isMostlyFillingViewport);
+}
+
 void WebMediaPlayerImpl::DoLoad(LoadType load_type,
                                 const blink::WebURL& url,
                                 CORSMode cors_mode) {