[SyncFS] Make DumpFiles async

chrome/browser/sync_file_system/sync_file_system_service.cc

Index: chrome/browser/sync_file_system/sync_file_system_service.cc
diff --git a/chrome/browser/sync_file_system/sync_file_system_service.cc b/chrome/browser/sync_file_system/sync_file_system_service.cc
index 9f19c7e7a415bf882bbf793ae13024a68d977825..e9f33d1f2fd88f28d7d10ae18b993705ed1ab12c 100644
--- a/chrome/browser/sync_file_system/sync_file_system_service.cc
+++ b/chrome/browser/sync_file_system/sync_file_system_service.cc
@@ -513,8 +513,20 @@ void SyncFileSystemService::DidInitializeFileSystemForDump(
     return;
   }
 
-  base::ListValue* files =
-      GetRemoteService(origin)->DumpFiles(origin).release();
+  GetRemoteService(origin)->DumpFiles(
+      origin,
+      base::Bind(
+          &SyncFileSystemService::DidDumpFiles,
+          AsWeakPtr(),
+          origin,
+          callback));
+}
+
+void SyncFileSystemService::DidDumpFiles(
+    const GURL& origin,
+    const DumpFilesCallback& callback,
+    scoped_ptr<base::ListValue> dump_files) {
+  base::ListValue* files = dump_files.release();
   if (!files) {
     callback.Run(new base::ListValue);
     return;