Mojo: Add basic logging facilities to environment.

mojo/environment/default_logger.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/public/cpp/environment/default_async_waiter.h"
+#include "mojo/public/cpp/environment/default_logger.h"
 
-#include "mojo/environment/default_async_waiter_impl.h"
+#include "mojo/environment/default_logger_impl.h"
 
 namespace mojo {
 
-MojoAsyncWaiter* GetDefaultAsyncWaiter() {
-  return internal::GetDefaultAsyncWaiterImpl();
+const MojoLogger* GetDefaultLogger() {
+  return internal::GetDefaultLoggerImpl();
 }
 
 }  // namespace mojo