EDK: Make mojo::embedder::AsyncWait (etc.) take an std::function instead of a base::Callback.

mojo/edk/system/async_waiter.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/edk/system/async_waiter.h"
 
 namespace mojo {
 namespace system {
 
 AsyncWaiter::AsyncWaiter(const AwakeCallback& callback) : callback_(callback) {
 }
 
 AsyncWaiter::~AsyncWaiter() {
 }
 
 bool AsyncWaiter::Awake(MojoResult result, uintptr_t context) {
-  callback_.Run(result);
+  callback_(result);
   delete this;
   return false;
 }
 
 }  // namespace system
 }  // namespace mojo