[USS] Show USS counters in about:sync page

components/sync/core/shared_model_type_processor.cc

Index: components/sync/core/shared_model_type_processor.cc
diff --git a/components/sync/core/shared_model_type_processor.cc b/components/sync/core/shared_model_type_processor.cc
index 85475769c889196ab6e59c3caa382d54b8758dd9..39065d405ac0fc0707661a2bfb9f86c6f4a51e3e 100644
--- a/components/sync/core/shared_model_type_processor.cc
+++ b/components/sync/core/shared_model_type_processor.cc
@@ -202,6 +202,24 @@ void SharedModelTypeProcessor::GetAllNodes(
                  base::Unretained(this), task_runner, callback));
 }
 
+void SharedModelTypeProcessor::GetStatusCounters(
+    const scoped_refptr<base::TaskRunner>& task_runner,
+    const base::Callback<void(syncer::ModelType,
+                              std::unique_ptr<syncer::StatusCounters>)>
+        callback) {
+  DCHECK(CalledOnValidThread());
+  std::unique_ptr<syncer::StatusCounters> counters =
+      base::MakeUnique<syncer::StatusCounters>();
+  for (auto it = entities_.begin(); it != entities_.end(); ++it) {
+    ++counters->num_entries_and_tombstones;
+    if (!it->second->metadata().is_deleted()) {
+      ++counters->num_entries;
+    }
+  }
+  task_runner->PostTask(FROM_HERE,
+                        base::Bind(callback, type_, base::Passed(&counters)));
+}
+
 void SharedModelTypeProcessor::DisableSync() {
   DCHECK(CalledOnValidThread());
   std::unique_ptr<MetadataChangeList> change_list =