Introduce MetricsServiceClient::StartGatheringMetrics

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 64bdcfc1a57a64dcfcfa0c970c8c1cc463cb89d4..891b90f6b9190c04784787f380bfbff10e7a9bbe 100644
--- a/components/metrics/test_metrics_service_client.cc
+++ b/components/metrics/test_metrics_service_client.cc
@@ -45,6 +45,11 @@ std::string TestMetricsServiceClient::GetVersionString() {
 void TestMetricsServiceClient::OnLogUploadComplete() {
 }
 
+void TestMetricsServiceClient::StartGatheringMetrics(
+    const base::Closure& done_callback) {
+  done_callback.Run();
+}
+
 void TestMetricsServiceClient::CollectFinalMetrics(
     const base::Closure& done_callback) {
   done_callback.Run();