Autofill: Use field maxlength to improve credit card date matching.

components/autofill/core/browser/credit_card_field.cc

Index: components/autofill/core/browser/credit_card_field.cc
diff --git a/components/autofill/core/browser/credit_card_field.cc b/components/autofill/core/browser/credit_card_field.cc
index 0e8d25dbfa58483b0badab61796a48d2e6a59a9d..d0b0e28e549ef87aec4462efc2802734a41b21fd 100644
--- a/components/autofill/core/browser/credit_card_field.cc
+++ b/components/autofill/core/browser/credit_card_field.cc
@@ -362,6 +362,15 @@ bool CreditCardField::ParseExpirationDate(AutofillScanner* scanner) {
   // Look for a 2-digit year first.
   // We allow <select> fields, because they're used e.g. on qvc.com.
   scanner->RewindTo(month_year_saved_cursor);
+
+  static int kMinimum4YearCcExpLength = strlen("2014-12");

[Evan Stade, 2015/04/01 23:08:27]

I guess it's a nit but why is this 2014-12 instead of 12/2014? We'll actually
fill 12/2014, so that's the example you should use.

also, second nit: define this where it's actually used

[Lei Zhang, 2015/04/02 00:30:13]

Done.

+  static int kMinimum2YearCcExpLength = strlen("12/14");
+  int current_field_max_length = scanner->Cursor()->max_length;
+  if (current_field_max_length > 0 &&
+      current_field_max_length < kMinimum2YearCcExpLength) {
+    return false;
+  }
+
   if (ParseFieldSpecifics(scanner,
                           base::UTF8ToUTF16(kExpirationDate2DigitYearRe),
                           kMatchTelAndSelect,
@@ -371,10 +380,15 @@ bool CreditCardField::ParseExpirationDate(AutofillScanner* scanner) {
     return true;
   }
 
+
   if (ParseFieldSpecifics(scanner,
                           base::UTF8ToUTF16(kExpirationDateRe),
                           kMatchTelAndSelect,
                           &expiration_date_)) {
+    if (current_field_max_length > 0 &&

[Evan Stade, 2015/04/01 23:08:26]

for consistency with the 2digit year case, shouldn't you move this to before the
ParseFieldSpecifics

[Lei Zhang, 2015/04/02 00:30:13]

|kExpirationDateRe| isn't only for 4 digit years. Previously, we've assumed this
will always be a 4 digit year field, but now we check the length and change the
type if necessary.

+        current_field_max_length < kMinimum4YearCcExpLength) {
+      exp_year_type_ = CREDIT_CARD_EXP_DATE_2_DIGIT_YEAR;
+    }
     expiration_month_ = nullptr;
     return true;
   }