Coverity: Fix a few pass-by-values.

chrome/browser/autofill/autofill_external_delegate.cc

 // 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.
 
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/autofill/autofill_external_delegate.h"
 #include "chrome/browser/autofill/autofill_manager.h"
 #include "chrome/browser/ui/tab_contents/tab_contents_wrapper.h"
 #include "chrome/common/autofill_messages.h"
 #include "chrome/common/chrome_constants.h"
@@ skipping 120 matching lines @@
 
   tab_contents_wrapper_->autofill_manager()->OnDidShowAutofillSuggestions(
       has_autofill_item && !has_shown_autofill_popup_for_current_edit_);
   has_shown_autofill_popup_for_current_edit_ |= has_autofill_item;
 }
 
 void AutofillExternalDelegate::DidEndTextFieldEditing() {
   has_shown_autofill_popup_for_current_edit_ = false;
 }
 
-void AutofillExternalDelegate::DidAcceptAutofillSuggestions(string16 value,
-                                                            int unique_id,
-                                                            unsigned index) {
+void AutofillExternalDelegate::DidAcceptAutofillSuggestions(
+    const string16& value, int unique_id, unsigned index) {
   // If the selected element is a warning we don't want to do anything.
   if (unique_id < 0)
     return;
 
   // TODO(csharp): Add the password autofill manager.
   // if (password_autofill_manager_->DidAcceptAutofillSuggestion(node, value))
   //   return;
 
   if (suggestions_options_index_ != -1 &&
       index == static_cast<unsigned>(suggestions_options_index_)) {
@@ skipping 57 matching lines @@
 // none, so all platforms use the default.
 
 #if !defined(OS_ANDROID) && !defined(TOOLKIT_GTK)
 
 AutofillExternalDelegate* AutofillExternalDelegate::Create(
     TabContentsWrapper*, AutofillManager*) {
   return NULL;
 }
 
 #endif