[Autofill] Add the phone extension type.

components/autofill/core/browser/phone_number.cc

Index: components/autofill/core/browser/phone_number.cc
diff --git a/components/autofill/core/browser/phone_number.cc b/components/autofill/core/browser/phone_number.cc
index 550b1065e878bfec862aa2cf1d7d694a686d5df5..d09117d201814eec96044e7af6457e1786db50bb 100644
--- a/components/autofill/core/browser/phone_number.cc
+++ b/components/autofill/core/browser/phone_number.cc
@@ -119,6 +119,9 @@ base::string16 PhoneNumber::GetInfo(const AutofillType& type,
       return
           cached_parsed_phone_.city_code() + cached_parsed_phone_.number();
 
+    case PHONE_HOME_EXTENSION:
+      return base::string16();
+
     default:
       NOTREACHED();
       return base::string16();