[Autofill] Add upstreaming UKM

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 540d4c5eefd64fa0fbb9671df66d80f620d653a3..72c923afc837ced52a78a7bd3256830a343e78b7 100644
--- a/components/ukm/ukm_service.h
+++ b/components/ukm/ukm_service.h
@@ -24,6 +24,10 @@ class PrefRegistrySimple;
 class PrefService;
 class UkmPageLoadMetricsObserver;
 
+namespace autofill {
+class AutofillUkm;
+}  // namespace autofill
+
 namespace metrics {
 class MetricsLogUploader;
 class MetricsServiceClient;
@@ -105,6 +109,7 @@ class UkmService : public base::SupportsWeakPtr<UkmService> {
 
  private:
   friend UkmPageLoadMetricsObserver;
+  friend autofill::AutofillUkm;
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, AddEntryOnlyWithNonEmptyMetrics);
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, EntryBuilderAndSerialization);
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest,