Disable autocomplete with unknown autocomplete attribute value.

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 <stdint.h>
 
 #include <algorithm>
@@ skipping 565 matching lines @@
         if (!has_logged_address_suggestions_count_ && !section_is_autofilled) {
           AutofillMetrics::LogAddressSuggestionsCount(suggestions.size());
           has_logged_address_suggestions_count_ = true;
         }
       }
     }
   }
 
   // If there are no Autofill suggestions, consider showing Autocomplete
   // suggestions. We will not show Autocomplete suggestions for a field that
-  // specifies autocomplete=off or a field that we think is a credit card
-  // expiration, cvc or number.
+  // specifies autocomplete=off (or an unrecognized type) or a field that we
+  // think is a credit card expiration, cvc or number.
   if (suggestions.empty() && field.should_autocomplete &&
       !(autofill_field &&
         (IsCreditCardExpirationType(autofill_field->Type().GetStorableType()) ||
+         autofill_field->Type().html_type() == HTML_TYPE_UNRECOGNIZED ||
          autofill_field->Type().GetStorableType() == CREDIT_CARD_NUMBER ||
          autofill_field->Type().GetStorableType() ==
              CREDIT_CARD_VERIFICATION_CODE))) {
     // Suggestions come back asynchronously, so the Autocomplete manager will
     // handle sending the results back to the renderer.
     autocomplete_history_manager_->OnGetAutocompleteSuggestions(
         query_id, field.name, field.value, field.form_control_type);
     return;
   }
 
@@ skipping 1440 matching lines @@
     if (i > 0)
       fputs("Next oldest form:\n", file);
   }
   fputs("\n", file);
 
   fclose(file);
 }
 #endif  // ENABLE_FORM_DEBUG_DUMP
 
 }  // namespace autofill