[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 7247e4d4d80d1fa0b69078450c246f4b68884872..edf8c1b1e9ad291dc00e2aadfd45ce73ca5e06eb 100644
--- a/components/ukm/ukm_service.h
+++ b/components/ukm/ukm_service.h
@@ -29,6 +29,10 @@ namespace autofill {
 class AutofillMetrics;
 }  // namespace autofill
 
+namespace payments {
+class JourneyLogger;
+}  // namespace payments
+
 namespace metrics {
 class MetricsServiceClient;
 }
@@ -110,6 +114,7 @@ class UkmService {
 
  private:
   friend autofill::AutofillMetrics;
+  friend payments::JourneyLogger;
   friend PluginInfoMessageFilter;
   friend UkmPageLoadMetricsObserver;
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, AddEntryOnlyWithNonEmptyMetrics);