Move the thread hop for UMA user actions from content:: to base::.

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 7aeaddf9c695c3802e927ede89feab143c6f2545..77f4717d3e187bfe21ef08f6d5b68ae44c4a49fd 100644
--- a/components/metrics/test_metrics_service_client.cc
+++ b/components/metrics/test_metrics_service_client.cc
@@ -5,6 +5,7 @@
 #include "components/metrics/test_metrics_service_client.h"
 
 #include "base/callback.h"
+#include "base/test/test_simple_task_runner.h"
 #include "components/metrics/metrics_log_uploader.h"
 #include "components/metrics/proto/chrome_user_metrics_extension.pb.h"
 
@@ -17,7 +18,8 @@ TestMetricsServiceClient::TestMetricsServiceClient()
     : version_string_("5.0.322.0-64-devel"),
       product_(ChromeUserMetricsExtension::CHROME),
       reporting_is_managed_(false),
-      enable_default_(MetricsServiceClient::DEFAULT_UNKNOWN) {}
+      enable_default_(MetricsServiceClient::DEFAULT_UNKNOWN),
+      task_runner_(new base::TestSimpleTaskRunner) {}
 
 TestMetricsServiceClient::~TestMetricsServiceClient() {
 }
@@ -81,6 +83,11 @@ base::TimeDelta TestMetricsServiceClient::GetStandardUploadInterval() {
   return base::TimeDelta::FromMinutes(5);
 }
 
+scoped_refptr<base::SingleThreadTaskRunner>
+TestMetricsServiceClient::GetMainThreadTaskRunner() {
+  return task_runner_;
+}
+
 bool TestMetricsServiceClient::IsReportingPolicyManaged() {
   return reporting_is_managed_;
 }