Fix compiling of sync on linux.

chrome/browser/sync/util/user_settings_posix.cc

 // Copyright (c) 2009 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 entry.
 //
 // Implement the storage of service tokens in memory.
 
 #include "chrome/browser/sync/util/user_settings.h"
 
 namespace browser_sync {
 
 void UserSettings::ClearAllServiceTokens() {
   service_tokens_.clear();
 }
 
-void UserSettings::SetAuthTokenForService(const string& email,
-    const string& service_name, const string& long_lived_service_token) {
+void UserSettings::SetAuthTokenForService(
+    const std::string& email,
+    const std::string& service_name,
+    const std::string& long_lived_service_token) {
   service_tokens_[service_name] = long_lived_service_token;
 }
 
-bool UserSettings::GetLastUserAndServiceToken(const string& service_name,
-                                              string* username,
-                                              string* service_token) {
+bool UserSettings::GetLastUserAndServiceToken(const std::string& service_name,
+                                              std::string* username,
+                                              std::string* service_token) {
   ServiceTokenMap::const_iterator iter = service_tokens_.find(service_name);
 
   if (iter != service_tokens_.end()) {
     *username = email_;
     *service_token = iter->second;
     return true;
   }
 
   return false;
 }
 
 }  // namespace browser_sync