sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index bab6a66a426f4241388f0afb2a19fc62935fb459..91e65fe2caa5fbb14d23cfc33777183ad874914e 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -29272,7 +29272,15 @@ class WorkerContext extends EventTarget {
   @DocsEditable
   @SupportedBrowser(SupportedBrowser.CHROME)
   @Experimental
-  void requestFileSystem(int type, int size, [_FileSystemCallback successCallback, _ErrorCallback errorCallback]) native "WorkerContext_webkitRequestFileSystem_Callback";
+  void _requestFileSystem(int type, int size, [_FileSystemCallback successCallback, _ErrorCallback errorCallback]) native "WorkerContext_webkitRequestFileSystem_Callback";
+
+  Future<FileSystem> requestFileSystem(int type, int size) {
+    var completer = new Completer<FileSystem>();
+    _requestFileSystem(type, size,
+        (value) { completer.complete(value); },
+        (error) { completer.completeError(error); });
+    return completer.future;
+  }
 
   @DomName('WorkerContext.webkitRequestFileSystemSync')
   @DocsEditable