When credit card upload to Google Payments is blocked due
to missing CVC in checkout flow, offer upload by requesting CVC
from user.

BUG=707104

Review-Url: https://codereview.chromium.org/2789843004
Cr-Commit-Position: refs/heads/master@{#464603}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index cbccc4b..6ccbdb1 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -2484,6 +2484,11 @@
          autofill::kAutofillCreditCardLastUsedDateDisplay,
          kAutofillCreditCardLastUsedDateFeatureVariations,
          "AutofillCreditCardLastUsedDate")},
+    {"enable-autofill-credit-card-upload-cvc-prompt",
+     flag_descriptions::kEnableAutofillCreditCardUploadCvcPrompt,
+     flag_descriptions::kEnableAutofillCreditCardUploadCvcPromptDescription,
+     kOsDesktop,
+     FEATURE_VALUE_TYPE(autofill::kAutofillUpstreamRequestCvcIfMissing)},
 #if defined(OS_WIN)
     {"windows10-custom-titlebar",
      flag_descriptions::kWindows10CustomTitlebarName,