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

components/metrics/metrics_service_client.h

Index: components/metrics/metrics_service_client.h
diff --git a/components/metrics/metrics_service_client.h b/components/metrics/metrics_service_client.h
index cde60e2c78e0481bd61a07bc2075634011c5a156..2fc5aabbd31c8fdc51d57b4d5d9ebf1f01d01007 100644
--- a/components/metrics/metrics_service_client.h
+++ b/components/metrics/metrics_service_client.h
@@ -10,6 +10,7 @@
 
 #include "base/callback_forward.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/single_thread_task_runner.h"
 #include "base/strings/string16.h"
 #include "base/time/time.h"
 #include "components/metrics/proto/system_profile.pb.h"
@@ -99,6 +100,9 @@ class MetricsServiceClient {
   // Returns the standard interval between upload attempts.
   virtual base::TimeDelta GetStandardUploadInterval() = 0;
 
+  virtual scoped_refptr<base::SingleThreadTaskRunner>
+      GetUIThreadTaskRunner() = 0;

[Ilya Sherman, 2016/04/06 02:36:29]

Please document this method.

[Ilya Sherman, 2016/04/06 02:36:29]

nit: I think "MainThread" would be better than "UIThread".

[beaudoin, 2016/04/06 15:06:13]

Done.

[beaudoin, 2016/04/06 15:06:13]

Done.

+
   // Returns the name of a key under HKEY_CURRENT_USER that can be used to store
   // backups of metrics data. Unused except on Windows.
   virtual base::string16 GetRegistryBackupKey();