Reland mac symbol test.

tools/perf/core/stacktrace_unittest.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from telemetry.core import exceptions
 from telemetry import decorators
 from telemetry.testing import tab_test_case
 
 class TabStackTraceTest(tab_test_case.TabTestCase):
 
   # For now just work on a single platform (mac).
   @decorators.Enabled('mac')
    # Stack traces do not currently work on 10.6, but they are also being
    # disabled shortly so just disable it for now.
   @decorators.Disabled('snowleopard')
   def testStackTrace(self):
     try:
       self._tab.Navigate('chrome://crash', timeout=5)
     except exceptions.DevtoolsTargetCrashException as e:
       self.assertIn('Thread 0 (crashed)', '\n'.join(e.stack_trace))
 
   # Currently stack traces do not work on windows: http://crbug.com/476110
-  # Currently symbols do not work on swarming: http://crbug.com/563716
   # Linux stack traces depends on fission support: http://crbug.com/405623
-  @decorators.Disabled('all')
+  @decorators.Enabled('mac')
+  @decorators.Disabled('snowleopard')
   def testCrashSymbols(self):
     try:
       self._tab.Navigate('chrome://crash', timeout=5)
     except exceptions.DevtoolsTargetCrashException as e:
       self.assertIn('CrashIntentionally', '\n'.join(e.stack_trace))