fixes #27586, prefer context type in generic inference

tests/lib_strong/html/documentfragment_test.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:html';
 
 import 'package:expect/minitest.dart';
 
 import 'util.dart';
 
@@ skipping 155 matching lines @@
   test('getting innerHtml works', () {
     var fragment = new DocumentFragment();
     fragment.nodes.addAll([new Text("foo"), new Element.html("<A>bar</A>")]);
     expect(fragment.innerHtml, "foo<a>bar</a>");
   });
 
   test('query searches the fragment', () {
     var fragment = new DocumentFragment.html(
       "<div class='foo'><a>foo</a><b>bar</b></div>");
     expect(fragment.query(".foo a").tagName, "A");
-    expect(_nodeStrings(fragment.queryAll(".foo *")), equals(["A", "B"]));
+    expect(_nodeStrings(fragment.queryAll<Element>(".foo *")),
+        equals(["A", "B"]));
   });
 }