Fix status for wheelevent_test on Safari

tests/html/html.status

 # Copyright (c) 2013, 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.
 
 async_window_test: Skip #TODO(gram): investigating
 event_test: Skip  # Issue 1996
 interactive_test: Skip # Must be run manually.
 
 [ $compiler == dart2js && $browser ]
 element_offset_test/offset: Pass, Fail # Issue 13296
@@ skipping 254 matching lines @@
 xsltprocessor_test/supported: Fail
 
 [ $runtime == safari ]
 worker_test: Skip # Issue 13221
 worker_api_test: Skip # Issue 13221
 element_types_test/supported_track: Pass, Fail
 input_element_test/supported_month: Fail, Crash
 input_element_test/supported_time: Fail, Crash
 input_element_test/supported_week: Fail, Crash
 webgl_1_test: Pass, Fail # Issue 8219
-wheelevent_test: Fail # Issue: 12798
 canvasrenderingcontext2d_test/drawImage_video_element: Fail # Safari does not support drawImage w/ video element
 canvasrenderingcontext2d_test/drawImage_video_element_dataUrl: Fail # Safari does not support drawImage w/ video element
 audiocontext_test/functional: Fail # Issue 14354
 
 
 # Safari Feature support statuses-
 # All changes should be accompanied by platform support annotation changes.
 element_types_test/supported_content: Fail
 element_types_test/supported_datalist: Fail
 element_types_test/supported_shadow: Fail
@@ skipping 107 matching lines @@
 postmessage_structured_test: Skip  # Test cannot run under CSP restrictions (times out).
 
 [ $compiler == dart2js && $runtime == drt ]
 wheelevent_test: Fail # http://dartbug.com/12958
 
 [ $compiler == none && $runtime == dartium ]
 async_test: Timeout # Issue 13719: Please triage this failure.
 dromaeo_smoke_test: Fail # Issue 13719: Please triage this failure.
 element_offset_test/offset: Pass, Fail # Issue 13719, 13296
 touchevent_test/supported: Fail # Issue 13719: Please triage this failure.