Move IsRunningOnChromeOS to base/chromeos

chrome/browser/chromeos/system/runtime_environment.cc

-// Copyright (c) 2011 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/chromeos/system/runtime_environment.h"
-
-#include <stdlib.h>
-#include <string.h>
-
-#include "base/logging.h"
-
-namespace chromeos {
-namespace system {
-namespace runtime_environment {
-
-bool IsRunningOnChromeOS() {
-  // Check if the user name is chronos. Note that we don't go with
-  // getuid() + getpwuid_r() as it may end up reading /etc/passwd, which
-  // can be expensive.
-  const char* user = getenv("USER");
-  return user && strcmp(user, "chronos") == 0;
-}
-
-}  // namespace runtime_environment
-}  // namespace system
-}  // namespace chromeos