Some unit test fixes

tests/html/html.status

 # Copyright (c) 2012, 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.
 
 event_test: Skip  # Issue 1996
 webgl_1_test: Skip  # Issue 1495
 xmldocument_test: Skip  # XML in dart:html is incomplete
 xmlelement_test: Skip  # XML in dart:html is incomplete
 measurement_test: Pass, Fail  # Issue 1940
 
@@ skipping 141 matching lines @@
 # Unknown error - should investigate.
 element_test: Fail
 measurement_test: Fail
 
 [ $compiler == dart2js && $runtime == none ]
 *: Fail, Pass # TODO(ahe): Triage these tests.
 
 [ $compiler == dart2js ]
 dom_isolates_test: Fail # error: cannot resolve spawnDomIsolate
 svgelement2_test: Fail # Html library relies on mangling. Issue 3039.
+transferables_test: Skip # until isInstance works in dart2js
 
 [ $compiler == dart2js && $runtime == d8 ]
 # Should investigate why this test succeeds on d8.
 svgelement2_test: Pass
 
 [ $compiler == dart2js && ($runtime == drt || $runtime == ff) ]
 request_animation_frame_test: Skip # Async test hangs.
 
 [ $compiler == dart2js && ($runtime == drt || $runtime == chrome || $runtime == ff) ]
 isolates_test: Skip   # Timeout because leg does not support web workers.
@@ skipping 24 matching lines @@
 
 [ $compiler == dart2js && $runtime == chrome && $system == windows]
 css_test: Pass, Fail # Issue #2823
 element_test: Fail # method not found: 'get$add'
 fileapi_test: Skip # Issue 3022
 
 [ $compiler == dart2js && $runtime == drt && $system == macos ]
 indexeddb_2_test: Fail # Issue 3669.
 indexeddb_3_test: Fail # Issue 3670.
 window_open_test: Fail # Issue 3671.