Coverity: Fix pass by value error.

chrome/common/extensions/extension_permission_set.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_EXTENSION_PERMISSION_SET_H_
 #define CHROME_COMMON_EXTENSIONS_EXTENSION_PERMISSION_SET_H_
 #pragma once
 
 #include <map>
 #include <set>
@@ skipping 213 matching lines @@
 class ExtensionPermissionsInfo {
  public:
   // Returns a pointer to the singleton instance.
   static ExtensionPermissionsInfo* GetInstance();
 
   // Returns the permission with the given |id|, and NULL if it doesn't exist.
   ExtensionAPIPermission* GetByID(ExtensionAPIPermission::ID id);
 
   // Returns the permission with the given |name|, and NULL if none
   // exists.
-  ExtensionAPIPermission* GetByName(std::string name);
+  ExtensionAPIPermission* GetByName(const std::string& name);
 
   // Returns a set containing all valid api permission ids.
   ExtensionAPIPermissionSet GetAll();
 
   // Converts all the permission names in |permission_names| to permission ids.
   ExtensionAPIPermissionSet GetAllByName(
       const std::set<std::string>& permission_names);
 
   // Gets the total number of API permissions.
   size_t get_permission_count() { return permission_count_; }
@@ skipping 202 matching lines @@
 
   // The list of hosts this effectively grants access to.
   URLPatternSet effective_hosts_;
 
   // A set of oauth2 scopes that are used by the identity API to create OAuth2
   // tokens for accessing the Google Account of the signed-in sync account.
   ExtensionOAuth2Scopes scopes_;
 };
 
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_PERMISSION_SET_H_