[USS] Show USS counters in about:sync page

components/sync/driver/non_blocking_data_type_controller.cc

Index: components/sync/driver/non_blocking_data_type_controller.cc
diff --git a/components/sync/driver/non_blocking_data_type_controller.cc b/components/sync/driver/non_blocking_data_type_controller.cc
index a01905d7af7ca012dead37a7230d33d9192bc539..c28d4810298a3a30cf2e9e1afe9ea3a791192757 100644
--- a/components/sync/driver/non_blocking_data_type_controller.cc
+++ b/components/sync/driver/non_blocking_data_type_controller.cc
@@ -91,6 +91,23 @@ void NonBlockingDataTypeController::GetAllNodes(
                               base::ThreadTaskRunnerHandle::Get(), callback));
 }
 
+void NonBlockingDataTypeController::GetStatusCounters(
+    const StatusCountersCallback& callback) {
+  base::WeakPtr<syncer_v2::ModelTypeService> service =
+      sync_client_->GetModelTypeServiceForType(type());
+  // TODO(gangwu): Casting should happen "near" where the processor factory has
+  // code that instantiates a new processor.
+  syncer_v2::SharedModelTypeProcessor* processor =
+      (syncer_v2::SharedModelTypeProcessor*)service->change_processor();
+  if (processor != nullptr) {
+    RunOnModelThread(
+        FROM_HERE,
+        base::Bind(&syncer_v2::SharedModelTypeProcessor::GetStatusCounters,
+                   base::Unretained(processor),

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

Why is it safe to pass processor as Unretained pointer? What if meanwhile model
type calls clear_change_processor() before this callback gets a chance to run?
Let's discuss it on tomorrow's standup meeting.

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

Done.

+                   base::ThreadTaskRunnerHandle::Get(), callback));
+  }
+}
+
 void NonBlockingDataTypeController::LoadModelsDone(
     ConfigureResult result,
     const syncer::SyncError& error) {