Add histogram for "scan credit card" usage.

components/autofill/core/browser/autofill_metrics.cc

Index: components/autofill/core/browser/autofill_metrics.cc
diff --git a/components/autofill/core/browser/autofill_metrics.cc b/components/autofill/core/browser/autofill_metrics.cc
index 32dc930ea63730ecf6d5e9b7ed039a5ac9136e65..8044c32d2b36d095cf9be497c81a2765c57f275d 100644
--- a/components/autofill/core/browser/autofill_metrics.cc
+++ b/components/autofill/core/browser/autofill_metrics.cc
@@ -273,6 +273,14 @@ void AutofillMetrics::LogCreditCardInfoBarMetric(InfoBarMetric metric) {
 }
 
 // static
+void AutofillMetrics::LogScanCreditCardPromptMetric(
+    ScanCreditCardPromptMetric metric) {
+  DCHECK_LT(metric, NUM_SCAN_CREDIT_CARD_PROMPT_METRICS);
+  UMA_HISTOGRAM_ENUMERATION("Autofill.ScanCreditCardPrompt", metric,
+                            NUM_SCAN_CREDIT_CARD_PROMPT_METRICS);
+}
+
+// static
 void AutofillMetrics::LogDialogDismissalState(DialogDismissalState state) {
   UMA_HISTOGRAM_ENUMERATION("RequestAutocomplete.DismissalState",
                             state, NUM_DIALOG_DISMISSAL_STATES);