[SyncFS] Make GetOriginStatusMap asynchronous

chrome/browser/sync_file_system/drive_backend/sync_worker.cc

Index: chrome/browser/sync_file_system/drive_backend/sync_worker.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/sync_worker.cc b/chrome/browser/sync_file_system/drive_backend/sync_worker.cc
index e803138cc63f54dc31a50d9a61ba763ebaeb0f3f..da55f1766503d1c0b18efc80687435456e3b1602 100644
--- a/chrome/browser/sync_file_system/drive_backend/sync_worker.cc
+++ b/chrome/browser/sync_file_system/drive_backend/sync_worker.cc
@@ -204,8 +204,8 @@ RemoteServiceState SyncWorker::GetCurrentState() const {
 }
 
 void SyncWorker::GetOriginStatusMap(
-    RemoteFileSyncService::OriginStatusMap* status_map) {
-  DCHECK(status_map);
+    const RemoteFileSyncService::StatusMapCallback& callback) {
+  RemoteFileSyncService::OriginStatusMap status_map;
 
   if (!GetMetadataDatabase())
     return;
@@ -216,12 +216,12 @@ void SyncWorker::GetOriginStatusMap(
   for (std::vector<std::string>::const_iterator itr = app_ids.begin();
        itr != app_ids.end(); ++itr) {
     const std::string& app_id = *itr;
-    GURL origin =
-        extensions::Extension::GetBaseURLFromExtensionId(app_id);
-    (*status_map)[origin] =
-        GetMetadataDatabase()->IsAppEnabled(app_id) ?
+    GURL origin = extensions::Extension::GetBaseURLFromExtensionId(app_id);
+    status_map[origin] = GetMetadataDatabase()->IsAppEnabled(app_id) ?
         "Enabled" : "Disabled";
   }
+
+  callback.Run(status_map);
 }
 
 scoped_ptr<base::ListValue> SyncWorker::DumpFiles(const GURL& origin) {