[autofill] Credit card scanning fixes and enhancements.

- Do not hide the 'scan new card' popup on every character typed.
- Show 'scan new card' only when user is typing digits or separators.
- Hide 'scan new card' suggestion after user typed in 6 digits.

BUG=449646, 441536

Review URL: https://codereview.chromium.org/857633003

Cr-Commit-Position: refs/heads/master@{#312009}

chrome/browser/ui/autofill/autofill_popup_controller_impl.cc

@@ -565,7 +565,8 @@ bool AutofillPopupControllerImpl::HasSuggestions() {
          id == POPUP_ITEM_ID_AUTOCOMPLETE_ENTRY ||
          id == POPUP_ITEM_ID_PASSWORD_ENTRY ||
          id == POPUP_ITEM_ID_DATALIST_ENTRY ||
-         id == POPUP_ITEM_ID_MAC_ACCESS_CONTACTS;
+         id == POPUP_ITEM_ID_MAC_ACCESS_CONTACTS ||
+         id == POPUP_ITEM_ID_SCAN_CREDIT_CARD;
 }
 
 void AutofillPopupControllerImpl::SetValues(

components/autofill/core/browser/autofill_manager.cc

@@ -299,8 +299,15 @@ bool AutofillManager::ShouldShowScanCreditCard(const FormData& form,
     return false;
 
   AutofillField* autofill_field = GetAutofillField(form, field);
-  return autofill_field &&
-         autofill_field->Type().GetStorableType() == CREDIT_CARD_NUMBER;
+  if (!autofill_field ||
+      autofill_field->Type().GetStorableType() != CREDIT_CARD_NUMBER) {
+    return false;
+  }
+
+  static const int kShowScanCreditCardMaxValueLength = 6;
+  return field.value.size() <= kShowScanCreditCardMaxValueLength &&
+         base::ContainsOnlyChars(CreditCard::StripSeparators(field.value),
+                                 base::ASCIIToUTF16("0123456789"));
 }
 
 bool AutofillManager::OnFormSubmitted(const FormData& form,