Eliminate //chrome dependencies from MetricsServicesManager

components/metrics/test_metrics_service_client.cc

Index: components/metrics/test_metrics_service_client.cc
diff --git a/components/metrics/test_metrics_service_client.cc b/components/metrics/test_metrics_service_client.cc
index 4275db81a71c5e3d3e6ab63dfad39fb28a7b396b..2f33bc7cec6d4293368ad1d533cf5e535fab1169 100644
--- a/components/metrics/test_metrics_service_client.cc
+++ b/components/metrics/test_metrics_service_client.cc
@@ -21,6 +21,10 @@ TestMetricsServiceClient::TestMetricsServiceClient()
 TestMetricsServiceClient::~TestMetricsServiceClient() {
 }
 
+metrics::MetricsService* TestMetricsServiceClient::GetMetricsService() {
+  return nullptr;
+}
+
 void TestMetricsServiceClient::SetMetricsClientId(
     const std::string& client_id) {
   client_id_ = client_id;