Basic UkmService implementation

chrome/browser/metrics/chrome_metrics_service_client.h

Index: chrome/browser/metrics/chrome_metrics_service_client.h
diff --git a/chrome/browser/metrics/chrome_metrics_service_client.h b/chrome/browser/metrics/chrome_metrics_service_client.h
index cc7e966e77a35f2eaac25cbe8fb0b69594a4284d..9266b1fb966afdfc5a01b63c4e8ab5e3da2eb002 100644
--- a/chrome/browser/metrics/chrome_metrics_service_client.h
+++ b/chrome/browser/metrics/chrome_metrics_service_client.h
@@ -61,6 +61,7 @@ class ChromeMetricsServiceClient
 
   // metrics::MetricsServiceClient:
   metrics::MetricsService* GetMetricsService() override;
+  ukm::UkmService* GetUkmService() override;
   void SetMetricsClientId(const std::string& client_id) override;
   int32_t GetProduct() override;
   std::string GetApplicationLocale() override;
@@ -152,6 +153,9 @@ class ChromeMetricsServiceClient
   // The MetricsService that |this| is a client of.
   std::unique_ptr<metrics::MetricsService> metrics_service_;
 
+  // The UkmService that |this| is a client of.
+  std::unique_ptr<ukm::UkmService> ukm_service_;
+
   content::NotificationRegistrar registrar_;
 
 #if defined(OS_CHROMEOS)