Cleanup: Pass std::string as const reference if possible

chrome/browser/extensions/activity_log/activity_actions.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_ACTIONS_H_
 #define CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_ACTIONS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 49 matching lines @@
   // The time the record was generated (or some approximation).
   const base::Time& time() const { return time_; }
   void set_time(const base::Time& time) { time_ = time; }
 
   // The ActionType distinguishes different classes of actions that can be
   // logged, and determines which other fields are expected to be filled in.
   ActionType action_type() const { return action_type_; }
 
   // The specific API call used or accessed, for example "chrome.tabs.get".
   const std::string& api_name() const { return api_name_; }
-  void set_api_name(const std::string api_name) { api_name_ = api_name; }
+  void set_api_name(const std::string& api_name) { api_name_ = api_name; }
 
   // Any applicable arguments.  This might be null to indicate no data
   // available (a distinct condition from an empty argument list).
   // mutable_args() returns a pointer to the list stored in the Action which
   // can be modified in place; if the list was null an empty list is created
   // first.
   const base::ListValue* args() const { return args_.get(); }
   void set_args(scoped_ptr<base::ListValue> args);
   base::ListValue* mutable_args();
 
@@ skipping 81 matching lines @@
 // comparisons.
 struct ActionComparatorExcludingTimeAndActionId {
   // Evaluates the comparison lhs < rhs.
   bool operator()(const scoped_refptr<Action>& lhs,
                   const scoped_refptr<Action>& rhs) const;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_ACTIONS_H_