cleanup: pass string as const reference from c/b/extension/api

chrome/browser/extensions/api/developer_private/developer_private_api.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_BROWSER_EXTENSIONS_API_DEVELOPER_PRIVATE_DEVELOPER_PRIVATE_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_DEVELOPER_PRIVATE_DEVELOPER_PRIVATE_API_H_
 
 #include <set>
 
 #include "base/files/file.h"
@@ skipping 260 matching lines @@
  public:
   DECLARE_EXTENSION_FUNCTION("developerPrivate.enable",
                              DEVELOPERPRIVATE_ENABLE);
 
   DeveloperPrivateEnableFunction();
 
  protected:
   virtual ~DeveloperPrivateEnableFunction();
 
   // Callback for requirements checker.
-  void OnRequirementsChecked(std::string extension_id,
+  void OnRequirementsChecked(const std::string& extension_id,
                              std::vector<std::string> requirements_errors);
   // ExtensionFunction:
   virtual bool RunSync() OVERRIDE;
 
  private:
   scoped_ptr<RequirementsChecker> requirements_checker_;
 };
 
 class DeveloperPrivateChooseEntryFunction : public ChromeAsyncExtensionFunction,
                                             public EntryPickerClient {
@@ skipping 169 matching lines @@
 
   // ExtensionFunction:
   virtual bool RunImpl() OVERRIDE;
 };
 
 }  // namespace api
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_DEVELOPER_PRIVATE_DEVELOPER_PRIVATE_API_H_