Basic UkmService implementation

ios/chrome/browser/metrics/ios_chrome_metrics_service_client.h

Index: ios/chrome/browser/metrics/ios_chrome_metrics_service_client.h
diff --git a/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.h b/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.h
index 20acfa77e5672779bbb800ed322c8c1d729fcd3f..9e036921fa3d128daa47d1f8c5c0a2ebdc9cff9c 100644
--- a/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.h
+++ b/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.h
@@ -29,6 +29,10 @@ class MetricsStateManager;
 class ProfilerMetricsProvider;
 }  // namespace metrics
 
+namespace ukm {
+class UkmService;
+}
+
 // IOSChromeMetricsServiceClient provides an implementation of
 // MetricsServiceClient that depends on //ios/chrome/.
 class IOSChromeMetricsServiceClient
@@ -47,6 +51,7 @@ class IOSChromeMetricsServiceClient
 
   // 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;
@@ -118,6 +123,9 @@ class IOSChromeMetricsServiceClient
   // 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_;
+
   // The IOSChromeStabilityMetricsProvider instance that was registered with
   // MetricsService. Has the same lifetime as |metrics_service_|.
   IOSChromeStabilityMetricsProvider* stability_metrics_provider_;