Refactoring datalist test to use the supported flag.

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.
 
 window_open_test: Skip # http://dartbug.com/5151
 
 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
@@ skipping 115 matching lines @@
 localstorage_test: Fail
 websql_test: Fail # IE does not support web SQL
 #
 # Investigate and triage the following into bug reports.
 #
 audiobuffersourcenode_test: Fail
 audiocontext_test: Fail
 blob_constructor_test: Fail
 cache_test: fail              # IE9 does not support ApplicationCache, but IE 10 does (and should work).
 css_test: Fail
-datalistelement_test: Fail    # ie9 does not have HTMLDataListElement
 dom_constructors_test: Fail
 element_test/additionalConstructors: Fail
 exceptions_test: Fail
 fileapi_test: Fail          # IE does not support filesystem APIs.
 history_test/supported_state: Fail
 indexeddb_1_test/supported: Fail
 input_element_test/supported_date: Fail
 input_element_test/supported_datetime-local: Fail
 input_element_test/supported_datetime: Fail
 input_element_test/supported_email: Fail
@@ skipping 32 matching lines @@
 performance_api_test: Fail # window.performance.timing not in Safari 6.
 indexeddb_1_test/supported: Fail
 input_element_test/supported_date: Fail
 input_element_test/supported_datetime: Fail
 input_element_test/supported_datetime-local: Fail
 input_element_test/supported_month: Fail, Crash
 input_element_test/supported_range: Fail, Crash    # TODO(efortuna): Please triage this failure.
 input_element_test/supported_time: Fail, Crash
 input_element_test/supported_week: Fail, Crash
 fileapi_test: Fail # requestFileSystem not supported in Safari 6.
-datalistelement_test: Fail # HTMLDataListElement not yet supported in Safari.
 # TODO(efortuna): Make our test framework able to separate tests out by browser
 # version.
-datalistelement_test: Fail # Issue: 7414
 node_test: Skip # Issue 6457
 
 [ $runtime == opera && $system == windows ]
 htmlelement_test: Fail, Pass
 
 [ $runtime == opera && $system == macos ]
 html/element_test/constructors: Fail
 
 
 [ $runtime == opera ]
@@ skipping 93 matching lines @@
 
 [ $compiler == dart2js && ($runtime == drt || $runtime == chrome || $runtime == ff || $runtime == safari) ]
 isolates_test: Skip   # Timeout because leg does not support web workers.
 typed_arrays_1_test: Fail # dart2js doesn't support is checks with generic types.
 
 [ $compiler == dart2js && $runtime == ff ]
 xhr_test: Skip # Timeout
 inner_frame_test: Skip # Timeout
 svg_3_test: Skip # Timeout
 documentfragment_test: Skip # Timeout