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 f8225d5e63171e5c7da3508237a17c8e950d56bc..842b860337c64cfd48970e683a8bce5ef33d700b 100644
--- a/content/browser/web_contents/web_contents_android.cc
+++ b/content/browser/web_contents/web_contents_android.cc
@@ -710,6 +710,12 @@ void WebContentsAndroid::SetHasPersistentVideo(
   web_contents_->SetHasPersistentVideo(value);
 }
 
+bool WebContentsAndroid::HasActiveEffectivelyFullscreenVideo(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jobject>& obj) {
+  return web_contents_->HasActiveEffectivelyFullscreenVideo();
+}
+
 void WebContentsAndroid::OnFinishGetContentBitmap(
     const JavaRef<jobject>& obj,
     const JavaRef<jobject>& callback,