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

chrome/common/extensions/csp_handler.cc

 // Copyright (c) 2013 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/common/extensions/csp_handler.h"
 
 #include "base/memory/scoped_ptr.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "chrome/common/extensions/csp_validator.h"
 #include "chrome/common/extensions/extension_manifest_constants.h"
 #include "chrome/common/extensions/manifest_handlers/sandboxed_page_info.h"
 
 namespace keys = extension_manifest_keys;
 namespace errors = extension_manifest_errors;
 
 using extensions::csp_validator::ContentSecurityPolicyIsLegal;
@@ skipping 105 matching lines @@
         type == Manifest::TYPE_LEGACY_PACKAGED_APP;
 }
 
 const std::vector<std::string> CSPHandler::Keys() const {
   const std::string& key = is_platform_app_ ?
       keys::kPlatformAppContentSecurityPolicy : keys::kContentSecurityPolicy;
   return SingleKey(key);
 }
 
 }  // namespace extensions