[Payments] Add PaymentRequest checkout funnel UKMs.

components/ukm/ukm_service.h

Index: components/ukm/ukm_service.h
diff --git a/components/ukm/ukm_service.h b/components/ukm/ukm_service.h
index 61f793925204a98cec28161d9503cba8ec5db4b9..1f5bb378c0f26ad6e9e1c5d361f74091b33d8680 100644
--- a/components/ukm/ukm_service.h
+++ b/components/ukm/ukm_service.h
@@ -33,6 +33,10 @@ namespace translate {
 class TranslateRankerImpl;
 }
 
+namespace payments {
+class JourneyLogger;
+}  // namespace payments
+
 namespace metrics {
 class MetricsServiceClient;
 }
@@ -114,6 +118,7 @@ class UkmService {
 
  private:
   friend autofill::AutofillMetrics;
+  friend payments::JourneyLogger;
   friend PluginInfoMessageFilter;
   friend UkmPageLoadMetricsObserver;
   friend translate::TranslateRankerImpl;