Adding supported checks and flags to window.performance.

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
 
 # Layout tests are only supported on DRT.
@@ skipping 134 matching lines @@
 xhr_cross_origin_test: Fail # Issue 6016.
 
 [ $runtime == safari ]
 # TODO(ahe, efortuna): These tests need to be retriaged now that we're testing
 # with Safari 6.
 audiocontext_test: Crash, Fail # Issue: 7414
 element_test/elements: Crash, Fail # Issue: 7414
 element_types_test/supported_content: Fail
 element_types_test/supported_datalist: Fail
 element_types_test/supported_shadow: Fail
-performance_api_test: Fail # window.performance.timing not in Safari 6.
+performance_api_test/supported: Fail
 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.
 node_test: Skip # Issue 6457
@@ skipping 19 matching lines @@
 element_constructor_1_test: Fail
 element_test/constructors: Fail
 element_test/elements: Fail
 element_test/eventListening: Crash
 element_test/queryAll: Fail
 element_webkit_test: Fail
 exceptions_test: Fail
 htmlelement_test: Fail
 indexeddb_1_test/supported: Fail
 mutationobserver_test/supported: Fail
-performance_api_test: Fail
+performance_api_test/supported: Fail
 serialized_script_value_test: Fail
 svg_3_test: Fail
 svgelement_test/additionalConstructors: Fail
 svgelement2_test: Fail
 typed_arrays_arraybuffer_test: Fail
 url_test: Fail
 fileapi_test: Skip # Timeout.
 inner_frame_test: Skip # Timeout.
 js_interop_3_test: Skip # Timeout.
 js_interop_4_test: Skip # Timeout.
@@ skipping 53 matching lines @@
 [ $compiler == dart2js && ($runtime == drt || $runtime == ff) ]
 request_animation_frame_test: Skip # Async test hangs.
 
 [ $compiler == dart2js && ($runtime == drt || $runtime == chrome || $runtime == ff || $runtime == safari) ]
 isolates_test: Skip   # Timeout because leg does not support web workers.
 
 [ $compiler == dart2js && $runtime == ff ]
 xhr_test: Skip # Timeout
 inner_frame_test: Skip # Timeout
 svg_3_test: Skip # Timeout