[USS] Show USS counters in about:sync page

components/sync/driver/directory_data_type_controller.cc

Index: components/sync/driver/directory_data_type_controller.cc
diff --git a/components/sync/driver/directory_data_type_controller.cc b/components/sync/driver/directory_data_type_controller.cc
index 62a1720ab5ecb0ba115c70a1d80ecd9cfdfd4ac8..b80875478227e0d1c15d8406d6a7c29f1350ce65 100644
--- a/components/sync/driver/directory_data_type_controller.cc
+++ b/components/sync/driver/directory_data_type_controller.cc
@@ -4,6 +4,8 @@
 
 #include "components/sync/driver/directory_data_type_controller.h"
 
+#include "base/memory/ptr_util.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "components/sync/core/user_share.h"
 #include "components/sync/driver/backend_data_type_configurer.h"
 #include "components/sync/driver/sync_service.h"
@@ -33,6 +35,26 @@ void DirectoryDataTypeController::GetAllNodes(
   callback.Run(type(), std::move(node_list));
 }
 
+void DirectoryDataTypeController::GetStatusCounters(
+    const StatusCountersCallback& callback) {
+  std::vector<int> num_entries_by_type(syncer::MODEL_TYPE_COUNT, 0);
+  std::vector<int> num_to_delete_entries_by_type(syncer::MODEL_TYPE_COUNT, 0);
+  sync_client_->GetSyncService()
+      ->GetUserShare()
+      ->directory->CollectMetaHandleCounts(&num_entries_by_type,
+                                           &num_to_delete_entries_by_type);
+  syncer::StatusCounters counters;
+  counters.num_entries_and_tombstones = num_entries_by_type[type()];
+  counters.num_entries =
+      num_entries_by_type[type()] - num_to_delete_entries_by_type[type()];
+
+  // do post here even already on UI thread, because need to send real counters

[pavely, 2016/10/03 21:40:14]

I attempted to rewrite this comment:
We post callback to current thread instead of calling it directly to ensure that
results of ProfileSyncService::GetTypeStatusMap are applied to UI before sync
counters collected here. Otherwise results of
ProfileSyncService::GetTypeStatusMap will overwrite counters with empty data.

[Gang Wu, 2016/10/06 00:20:22]

Done.

+  // for each data type after GetTypeStatusMap pass empty dictionary to UI.
+  // Otherwise UI will receive real counters first, then empty data.
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, base::Bind(callback, type(), counters));
+};
+
 void DirectoryDataTypeController::RegisterWithBackend(
     BackendDataTypeConfigurer* configurer) {}