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

chromecast/browser/metrics/cast_metrics_service_client.cc

Index: chromecast/browser/metrics/cast_metrics_service_client.cc
diff --git a/chromecast/browser/metrics/cast_metrics_service_client.cc b/chromecast/browser/metrics/cast_metrics_service_client.cc
index a6041cb60dcfa336a2651845a596cea994c165b7..e5215d63e913c8f3f900c7ccdad9d6a72e5103ef 100644
--- a/chromecast/browser/metrics/cast_metrics_service_client.cc
+++ b/chromecast/browser/metrics/cast_metrics_service_client.cc
@@ -33,6 +33,7 @@
 #include "components/metrics/url_constants.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
+#include "content/public/browser/browser_thread.h"
 #include "content/public/common/content_switches.h"
 
 #if defined(OS_LINUX)
@@ -260,6 +261,12 @@ base::TimeDelta CastMetricsServiceClient::GetStandardUploadInterval() {
   return base::TimeDelta::FromMinutes(kStandardUploadIntervalMinutes);
 }
 
+scoped_refptr<base::SingleThreadTaskRunner>
+CastMetricsServiceClient::GetMainThreadTaskRunner() {
+  return content::BrowserThread::GetMessageLoopProxyForThread(
+      content::BrowserThread::UI);
+}
+
 void CastMetricsServiceClient::EnableMetricsService(bool enabled) {
   if (!task_runner_->BelongsToCurrentThread()) {
     task_runner_->PostTask(