Provide a WebContents API to discover the playback of a fullscreen video.

content/browser/web_contents/web_contents_android.cc

Index: content/browser/web_contents/web_contents_android.cc
diff --git a/content/browser/web_contents/web_contents_android.cc b/content/browser/web_contents/web_contents_android.cc
index 8b225a63dcd6ce8537d6b40294c2f69a316b533d..8b9dfc9f35f593ab1c0aaf8e3087fa444617a400 100644
--- a/content/browser/web_contents/web_contents_android.cc
+++ b/content/browser/web_contents/web_contents_android.cc
@@ -726,6 +726,12 @@ void WebContentsAndroid::SetHasPersistentVideo(
   web_contents_->SetHasPersistentVideo(value);
 }
 
+bool WebContentsAndroid::HasActiveFullscreenDominantVideo(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jobject>& obj) {
+  return web_contents_->HasActiveFullscreenDominantVideo();
+}
+
 void WebContentsAndroid::OnFinishGetContentBitmap(
     const JavaRef<jobject>& obj,
     const JavaRef<jobject>& callback,