[USS] Show USS counters in about:sync page

components/sync/driver/sync_frontend.h

Index: components/sync/driver/sync_frontend.h
diff --git a/components/sync/driver/sync_frontend.h b/components/sync/driver/sync_frontend.h
index ae2239a33223cb6abcb4ba87218bc518abcfe9b1..2e39302f795b7aa479c72588fea46553fff37e0e 100644
--- a/components/sync/driver/sync_frontend.h
+++ b/components/sync/driver/sync_frontend.h
@@ -79,13 +79,14 @@ class SyncFrontend {
       syncer::ModelType type,
       const syncer::UpdateCounters& counters) = 0;
 
-  // Called when we receive an updated status counter for a directory type.
+  // Called when we receive an updated status counter for a datatype which is

[pavely, 2016/09/30 00:01:51]

I don't think this comment needs to elaborate kinds of datatypes.
Simply "Called when we receive an updated status counter for a datatype." should
be enough.

[Gang Wu, 2016/10/01 07:14:09]

Done.

+  // directory type or Unified Sync and Storage.
   //
   // Disabled by default.  Enable by calling
   // EnableDirectoryTypeDebugInfoForwarding() on the backend.
-  virtual void OnDirectoryTypeStatusCounterUpdated(
+  virtual void OnDatatypeStatusCounterUpdated(
       syncer::ModelType type,
-      const syncer::StatusCounters& counters) = 0;
+      std::unique_ptr<syncer::StatusCounters> counters) = 0;
 
   // The status of the connection to the sync server has changed.
   virtual void OnConnectionStatusChange(syncer::ConnectionStatus status) = 0;