Simplify Autofill Scanner semantics

chrome/browser/autofill/credit_card_field.cc

Index: chrome/browser/autofill/credit_card_field.cc
diff --git a/chrome/browser/autofill/credit_card_field.cc b/chrome/browser/autofill/credit_card_field.cc
index 13f5a89eaa94eb29d6984f128a61cc1026ad5e18..8d504f4bf667f52ddc7c0492ef6f48519ef6ca32 100644
--- a/chrome/browser/autofill/credit_card_field.cc
+++ b/chrome/browser/autofill/credit_card_field.cc
@@ -27,7 +27,7 @@ FormField* CreditCardField::Parse(AutofillScanner* scanner,
     return NULL;
 
   scoped_ptr<CreditCardField> credit_card_field(new CreditCardField);
-  scanner->SaveCursor();
+  size_t saved_cursor = scanner->SaveCursor();
 
   // Credit card fields can appear in many different orders.
   // We loop until no more credit card related fields are found, see |break| at
@@ -131,7 +131,7 @@ FormField* CreditCardField::Parse(AutofillScanner* scanner,
 
         if (!ParseFieldSpecifics(scanner, pattern, MATCH_DEFAULT | MATCH_SELECT,
                                  &credit_card_field->expiration_year_)) {
-          scanner->Rewind();
+          scanner->RewindTo(saved_cursor);
           return NULL;
         }
         continue;
@@ -179,7 +179,7 @@ FormField* CreditCardField::Parse(AutofillScanner* scanner,
     return credit_card_field.release();
   }
 
-  scanner->Rewind();
+  scanner->RewindTo(saved_cursor);
   return NULL;
 }