html_viewer: Add a mock WebNotificationManager.

mojo/services/html_viewer/blink_platform_impl.cc

 // Copyright 2014 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 "mojo/services/html_viewer/blink_platform_impl.h"
 
 #include <cmath>
 
 #include "base/command_line.h"
 #include "base/rand_util.h"
@@ skipping 251 matching lines @@
     blink::WebGestureDevice device_source,
     const blink::WebFloatPoint& velocity,
     const blink::WebSize& cumulative_scroll) {
   const bool is_main_thread = true;
   return ui::WebGestureCurveImpl::CreateFromDefaultPlatformCurve(
              gfx::Vector2dF(velocity.x, velocity.y),
              gfx::Vector2dF(cumulative_scroll.width, cumulative_scroll.height),
              is_main_thread).release();
 }
 
+blink::WebNotificationManager*
+BlinkPlatformImpl::notificationManager() {
+  return &web_notification_manager_;
+}
+
 // static
 void BlinkPlatformImpl::DestroyCurrentThread(void* thread) {
   WebThreadImplForMessageLoop* impl =
       static_cast<WebThreadImplForMessageLoop*>(thread);
   delete impl;
 }
 
 }  // namespace html_viewer