Add UMA stats to track whitelist download latency.

components/autofill/browser/autofill_metrics.h

Index: components/autofill/browser/autofill_metrics.h
diff --git a/components/autofill/browser/autofill_metrics.h b/components/autofill/browser/autofill_metrics.h
index 2f9abd03507ba1ea2b0c3ecb654929ebda093b35..e479714785ca1a5fce65371c6c716ba4185e27a1 100644
--- a/components/autofill/browser/autofill_metrics.h
+++ b/components/autofill/browser/autofill_metrics.h
@@ -350,6 +350,12 @@ class AutofillMetrics {
     NUM_WALLET_REQUIRED_ACTIONS
   };
 
+  // The success or failure of downloading Autocheckout whitelist file.
+  enum AutocheckoutWhitelistDownloadStatus {
+    AUTOCHECKOUT_WHITELIST_DOWNLOAD_FAILED,
+    AUTOCHECKOUT_WHITELIST_DOWNLOAD_SUCCEEDED,
+  };
+
   AutofillMetrics();
   virtual ~AutofillMetrics();
 
@@ -435,6 +441,11 @@ class AutofillMetrics {
       const base::TimeDelta& duration,
       AutocheckoutCompletionStatus status) const;
 
+  // Logs the time taken to download Autocheckout whitelist file.
+  virtual void LogAutocheckoutWhitelistDownloadDuration(
+      const base::TimeDelta& duration,
+      AutocheckoutWhitelistDownloadStatus status) const;
+
   // This should be called when a form that has been Autofilled is submitted.
   // |duration| should be the time elapsed between form load and submission.
   virtual void LogFormFillDurationFromLoadWithAutofill(