Fixing IndexedDB's deleteDatabase to have the correct future result.

sdk/lib/indexed_db/dartium/indexed_db_dartium.dart

Index: sdk/lib/indexed_db/dartium/indexed_db_dartium.dart
diff --git a/sdk/lib/indexed_db/dartium/indexed_db_dartium.dart b/sdk/lib/indexed_db/dartium/indexed_db_dartium.dart
index 15076fb6a4ef2adc23b6d7fc0ba6e72a5a11aa89..1a539d9b661ec11902a5f6d76f92ee17934c69a9 100644
--- a/sdk/lib/indexed_db/dartium/indexed_db_dartium.dart
+++ b/sdk/lib/indexed_db/dartium/indexed_db_dartium.dart
@@ -279,7 +279,14 @@ class IdbFactory extends NativeFieldWrapperClass1 {
       if (onBlocked != null) {
         request.onBlocked.listen(onBlocked);
       }
-      return _completeRequest(request);
+      var completer = new Completer.sync();
+      request.onSuccess.listen((e) {
+        completer.complete(this);
+      });
+      request.onError.listen((e) {
+        completer.completeError(e);
+      });
+      return completer.future;
     } catch (e, stacktrace) {
       return new Future.error(e, stacktrace);
     }