Use a direct include of strings headers in chrome/common/, part 1.

chrome/common/extensions/command.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROME_COMMON_EXTENSIONS_COMMAND_H_
 #define CHROME_COMMON_EXTENSIONS_COMMAND_H_
 
+#include <map>
 #include <string>
-#include <map>
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "ui/base/accelerators/accelerator.h"
 
 namespace base {
 class DictionaryValue;
 }
 
 namespace extensions {
 class Extension;
 }
 
@@ skipping 44 matching lines @@
   ui::Accelerator accelerator_;
   string16 description_;
 };
 
 // A mapping of command name (std::string) to a command object.
 typedef std::map<std::string, Command> CommandMap;
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_COMMAND_H_