Change other usages of .size() to .empty() when applicable.

chrome/browser/password_manager/password_store_mac.cc

 // Copyright (c) 2010 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/password_manager/password_store_mac.h"
 #include "chrome/browser/password_manager/password_store_mac_internal.h"
 
 #include <CoreServices/CoreServices.h>
 #include <set>
 #include <string>
@@ skipping 498 matching lines @@
     const PasswordForm& query_form) {
   std::string username = UTF16ToUTF8(query_form.username_value);
   std::vector<SecKeychainItemRef> matches =
       MatchingKeychainItems(query_form.signon_realm, query_form.scheme,
                             NULL, username.c_str());
   for (std::vector<SecKeychainItemRef>::iterator i = matches.begin();
        i != matches.end(); ++i) {
     keychain_->Free(*i);
   }
 
-  return matches.size() != 0;
+  return !matches.empty();
 }
 
 std::vector<PasswordForm*>
     MacKeychainPasswordFormAdapter::GetAllPasswordFormPasswords() {
   SecAuthenticationType supported_auth_types[] = {
     kSecAuthenticationTypeHTMLForm,
     kSecAuthenticationTypeHTTPBasic,
     kSecAuthenticationTypeHTTPDigest,
   };
 
@@ skipping 474 matching lines @@
   owned_keychain_adapter.SetFindsOnlyOwnedItems(true);
   for (std::vector<PasswordForm*>::const_iterator i = forms.begin();
        i != forms.end(); ++i) {
     owned_keychain_adapter.RemovePassword(**i);
   }
 }
 
 void PasswordStoreMac::CreateNotificationService() {
   notification_service_.reset(new NotificationService);
 }