[Autofill] Fill fields that have an autocomplete attributes even if not in a form.

components/autofill/core/browser/form_structure.cc

Index: components/autofill/core/browser/form_structure.cc
diff --git a/components/autofill/core/browser/form_structure.cc b/components/autofill/core/browser/form_structure.cc
index feb1ddc7dbb1755bb0a175bc3a3ce69c7afa1b31..bb8c3bd798804492192cb8a055d209d730ee9b3d 100644
--- a/components/autofill/core/browser/form_structure.cc
+++ b/components/autofill/core/browser/form_structure.cc
@@ -304,7 +304,8 @@ FormStructure::FormStructure(const FormData& form)
       has_author_specified_sections_(false),
       was_parsed_for_autocomplete_attributes_(false),
       has_password_field_(false),
-      is_form_tag_(form.is_form_tag) {
+      is_form_tag_(form.is_form_tag),
+      is_formless_checkout_(form.is_formless_checkout) {
   // Copy the form fields.
   std::map<base::string16, size_t> unique_names;
   for (const FormFieldData& field : form.fields) {
@@ -337,13 +338,15 @@ FormStructure::~FormStructure() {}
 
 void FormStructure::DetermineHeuristicTypes() {
   // First, try to detect field types based on each field's |autocomplete|
-  // attribute value.  If there is at least one form field that specifies an
-  // autocomplete type hint, don't try to apply other heuristics to match fields
-  // in this form.
+  // attribute value.
   if (!was_parsed_for_autocomplete_attributes_)
     ParseFieldTypesFromAutocompleteAttributes();
 
-  if (active_field_count() >= kRequiredFieldsForPredictionRoutines) {
+  // Then if there are enough active fields, and if we are dealing with either a
+  // proper <form> or a <form>-less checkout, run the heuristics and server
+  // prediction routines.
+  if (active_field_count() >= kRequiredFieldsForPredictionRoutines &&
+      (is_form_tag_ || is_formless_checkout_)) {
     ServerFieldTypeMap field_type_map;
     FormField::ParseFormFields(fields_.get(), is_form_tag_, &field_type_map);
     for (size_t i = 0; i < field_count(); ++i) {