[Coverity] Change some pass by values to pass by const refs.

chrome/browser/webdata/autofill_change.h

 // Copyright (c) 2011 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_WEBDATA_AUTOFILL_CHANGE_H__
 #define CHROME_BROWSER_WEBDATA_AUTOFILL_CHANGE_H__
 #pragma once
 
 #include "chrome/browser/webdata/autofill_entry.h"
 
@@ skipping 36 matching lines @@
 
 // Change notification details for Autofill profile changes.
 class AutofillProfileChange : public GenericAutofillChange<std::string> {
  public:
   // The |type| input specifies the change type.  The |key| input is the key,
   // which is expected to be the GUID identifying the |profile|.
   // When |type| == ADD, |profile| should be non-NULL.
   // When |type| == UPDATE, |profile| should be non-NULL.
   // When |type| == REMOVE, |profile| should be NULL.
   AutofillProfileChange(Type type,
-                        std::string key,
+                        const std::string& key,
                         const AutofillProfile* profile);
   virtual ~AutofillProfileChange();
 
   const AutofillProfile* profile() const { return profile_; }
   bool operator==(const AutofillProfileChange& change) const;
 
  private:
   // Weak reference, can be NULL.
   const AutofillProfile* profile_;
 };
 
 // Change notification details for Autofill credit card changes.
 class AutofillCreditCardChange : public GenericAutofillChange<std::string> {
  public:
   // The |type| input specifies the change type.  The |key| input is the key,
   // which is expected to be the GUID identifying the |credit_card|.
   // When |type| == ADD, |credit_card| should be non-NULL.
   // When |type| == UPDATE, |credit_card| should be non-NULL.
   // When |type| == REMOVE, |credit_card| should be NULL.
   AutofillCreditCardChange(Type type,
-                           std::string key,
+                           const std::string& key,
                            const CreditCard* credit_card);
   virtual ~AutofillCreditCardChange();
 
   const CreditCard* credit_card() const { return credit_card_; }
   bool operator==(const AutofillCreditCardChange& change) const;
 
  private:
   // Weak reference, can be NULL.
   const CreditCard* credit_card_;
 };
 
 #endif  // CHROME_BROWSER_WEBDATA_AUTOFILL_CHANGE_H__