[Autofill] Update the autocomplete types implementation to match the current HTML spec.

chrome/browser/autofill/autofill_field.h

Index: chrome/browser/autofill/autofill_field.h
diff --git a/chrome/browser/autofill/autofill_field.h b/chrome/browser/autofill/autofill_field.h
index 797802a83ae067fbac5cb161012fbcb646122a79..0b2109852f503d3b04931d57d556bf7077df5055 100644
--- a/chrome/browser/autofill/autofill_field.h
+++ b/chrome/browser/autofill/autofill_field.h
@@ -26,14 +26,14 @@ class AutofillField : public FormFieldData {
 
   const string16& unique_name() const { return unique_name_; }
 
-  const string16& section() const { return section_; }
+  const std::string& section() const { return section_; }
   AutofillFieldType heuristic_type() const { return heuristic_type_; }
   AutofillFieldType server_type() const { return server_type_; }
   const FieldTypeSet& possible_types() const { return possible_types_; }
   PhonePart phone_part() const { return phone_part_; }
 
   // Sets the heuristic type of this field, validating the input.
-  void set_section(const string16& section) { section_ = section; }
+  void set_section(const std::string& section) { section_ = section; }
   void set_heuristic_type(AutofillFieldType type);
   void set_server_type(AutofillFieldType type);
   void set_possible_types(const FieldTypeSet& possible_types) {
@@ -62,7 +62,7 @@ class AutofillField : public FormFieldData {
 
   // The unique identifier for the section (e.g. billing vs. shipping address)
   // that this field belongs to.
-  string16 section_;
+  std::string section_;
 
   // The type of the field, as determined by the Autofill server.
   AutofillFieldType server_type_;