Move MetricsService final log collection tasks to client.

components/metrics/test_metrics_service_client.cc

Index: components/metrics/test_metrics_service_client.cc
===================================================================
--- components/metrics/test_metrics_service_client.cc	(revision 272175)
+++ components/metrics/test_metrics_service_client.cc	(working copy)
@@ -4,6 +4,8 @@
 
 #include "components/metrics/test_metrics_service_client.h"
 
+#include "base/callback.h"
+
 namespace metrics {
 
 // static
@@ -43,4 +45,9 @@
 void TestMetricsServiceClient::OnLogUploadComplete() {
 }
 
+void TestMetricsServiceClient::CollectFinalMetrics(
+    const base::Closure& done_callback) {
+  done_callback.Run();
+}
+
 }  // namespace metrics