Push API: test that default notification is shown on Android when needed.

chrome/browser/push_messaging/push_messaging_service_observer_android.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/push_messaging/push_messaging_service_observer_android.h"
+
+#include "base/android/jni_android.h"
+#include "jni/PushMessagingServiceObserver_jni.h"
+
+// static
+bool PushMessagingServiceObserverAndroid::RegisterJni(JNIEnv* env) {
+  return chrome::android::RegisterNativesImpl(env);
+}
+
+void PushMessagingServiceObserverAndroid::OnMessageHandled() {
+  chrome::android::Java_PushMessagingServiceObserver_onMessageHandled(
+      base::android::AttachCurrentThread());
+}