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

chrome/browser/webdata/autofill_change.cc

 // 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.
 
 #include "chrome/browser/webdata/autofill_change.h"
 
 #include "chrome/browser/autofill/autofill_profile.h"
 #include "chrome/browser/autofill/credit_card.h"
 
 AutofillChange::AutofillChange(Type type, const AutofillKey& key)
     : GenericAutofillChange<AutofillKey>(type, key) {
 }
 
 AutofillChange::~AutofillChange() {
 }
 
 AutofillProfileChange::AutofillProfileChange(
-  Type type, std::string key, const AutofillProfile* profile)
+  Type type, const std::string& key, const AutofillProfile* profile)
     : GenericAutofillChange<std::string>(type, key),
       profile_(profile) {
   DCHECK(type == ADD ? (profile && profile->guid() == key) : true);
   DCHECK(type == UPDATE ? (profile && profile->guid() == key) : true);
   DCHECK(type == REMOVE ? !profile : true);
 }
 
 AutofillProfileChange::~AutofillProfileChange() {
 }
 
 bool AutofillProfileChange::operator==(
     const AutofillProfileChange& change) const {
   return type() == change.type() &&
          key() == change.key() &&
          (type() != REMOVE) ? *profile() == *change.profile() : true;
 }
 
 AutofillCreditCardChange::AutofillCreditCardChange(
-  Type type, std::string key, const CreditCard* credit_card)
+  Type type, const std::string& key, const CreditCard* credit_card)
     : GenericAutofillChange<std::string>(type, key), credit_card_(credit_card) {
   DCHECK(type == ADD ? (credit_card && credit_card->guid() == key) : true);
   DCHECK(type == UPDATE ? (credit_card && credit_card->guid() == key) : true);
   DCHECK(type == REMOVE ? !credit_card : true);
 }
 
 AutofillCreditCardChange::~AutofillCreditCardChange() {
 }
 
 bool AutofillCreditCardChange::operator==(
     const AutofillCreditCardChange& change) const {
   return type() == change.type() &&
          key() == change.key() &&
          (type() != REMOVE) ? *credit_card() == *change.credit_card() : true;
 }