[SyncFS] Make DumpFiles async

chrome/browser/sync_file_system/drive_backend/sync_engine.cc

Index: chrome/browser/sync_file_system/drive_backend/sync_engine.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/sync_engine.cc b/chrome/browser/sync_file_system/drive_backend/sync_engine.cc
index 82a03c753eac88eef7a8134e0945c31b5b5b0d86..124bfd495e2648bbffac64d4269956ec6deba672 100644
--- a/chrome/browser/sync_file_system/drive_backend/sync_engine.cc
+++ b/chrome/browser/sync_file_system/drive_backend/sync_engine.cc
@@ -301,9 +301,15 @@ void SyncEngine::GetOriginStatusMap(OriginStatusMap* status_map) {
   sync_worker_->GetOriginStatusMap(status_map);
 }
 
-scoped_ptr<base::ListValue> SyncEngine::DumpFiles(const GURL& origin) {
-  // TODO(peria): Make this route asynchronous.
-  return sync_worker_->DumpFiles(origin);
+void SyncEngine::DumpFiles(const GURL& origin,
+                           const ListCallback& callback) {
+  PostTaskAndReplyWithResult(
+      worker_task_runner_,
+      FROM_HERE,
+      base::Bind(&SyncWorker::DumpFiles,
+                 base::Unretained(sync_worker_.get()),
+                 origin),
+      callback);
 }
 
 scoped_ptr<base::ListValue> SyncEngine::DumpDatabase() {