Mark the single autofilled field when the relevant section is autofilled.

components/autofill/core/browser/autofill_manager.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_manager.h"
 
 #include <stddef.h>
 
 #include <limits>
 #include <map>
@@ skipping 551 matching lines @@
          iter != result.fields.end(); ++iter) {
       if ((*iter) == field) {
         base::string16 value = data_model->GetInfoForVariant(
             autofill_field->Type(), variant, app_locale_);
         if (AutofillField::FillFormField(
             *autofill_field, value, app_locale_, &(*iter))) {
           // Mark the cached field as autofilled, so that we can detect when a
           // user edits an autofilled field (for metrics).
           autofill_field->is_autofilled = true;
 
+          // Mark the field as autofilled when a non-empty value is assigned to
+          // it. This allows the renderer to distinguish autofilled fields from
+          // fields with non-empty values, such as select-one fields.
+          iter->is_autofilled = true;
+
           if (!is_credit_card && !value.empty())
             client_->DidFillOrPreviewField(value, profile_full_name);
         }
         break;
       }
     }
 
     driver_->SendFormDataToRenderer(query_id, action, result);
     return;
   }
@@ skipping 624 matching lines @@
     return false;
 
   // Disregard forms that we wouldn't ever autofill in the first place.
   if (!form.ShouldBeParsed(true))
     return false;
 
   return true;
 }
 
 }  // namespace autofill