Autofill dropdown icons:

components/autofill/core/browser/autofill_external_delegate.cc

 // Copyright 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.
 
 #include "components/autofill/core/browser/autofill_external_delegate.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
@@ skipping 93 matching lines @@
 
   // Add a separator to go between the values and menu items.
   values.push_back(base::string16());
   labels.push_back(base::string16());
   icons.push_back(base::string16());
   ids.push_back(POPUP_ITEM_ID_SEPARATOR);
 
   if (manager_->ShouldShowScanCreditCard(query_form_, query_field_)) {
     values.push_back(l10n_util::GetStringUTF16(IDS_AUTOFILL_SCAN_CREDIT_CARD));
     labels.push_back(base::string16());
-    icons.push_back(base::string16());
+    icons.push_back(base::ASCIIToUTF16("scanCreditCardIcon"));
     ids.push_back(POPUP_ITEM_ID_SCAN_CREDIT_CARD);
   }
 
   // Only include "Autofill Options" special menu item if we have Autofill
   // suggestions.
   has_suggestion_ = false;
   for (size_t i = 0; i < ids.size(); ++i) {
     if (ids[i] > 0) {
       has_suggestion_ = true;
       break;
@@ skipping 308 matching lines @@
                      POPUP_ITEM_ID_DATALIST_ENTRY);
 }
 
 #if defined(OS_MACOSX) && !defined(OS_IOS)
 void AutofillExternalDelegate::PingRenderer() {
   driver_->PingRenderer();
 }
 #endif  // defined(OS_MACOSX) && !defined(OS_IOS)
 
 }  // namespace autofill