Eliminate //chrome dependencies from MetricsServicesManager

ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc

Index: ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc
diff --git a/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc b/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc
index 06a353331a7490ffc967db6dc681d2cc5d46fa51..f96fa35211a98afb62f72885130024fee0123594 100644
--- a/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc
+++ b/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc
@@ -105,6 +105,10 @@ void IOSChromeMetricsServiceClient::RegisterPrefs(
   metrics::StabilityMetricsHelper::RegisterPrefs(registry);
 }
 
+metrics::MetricsService* IOSChromeMetricsServiceClient::GetMetricsService() {
+  return metrics_service_.get();
+}
+
 void IOSChromeMetricsServiceClient::SetMetricsClientId(
     const std::string& client_id) {
   crash_keys::SetMetricsClientIdFromGUID(client_id);