Url to the build Failure:
https://luci-milo.appspot.com/buildbot/chromium.webkit/WebKit Win10/21161

What is the bug or feature:
Traceback (most recent call last):
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts\slave\.recipe_deps\recipe_engine\recipe_engine\run.py", line 316, in _new_run
    recipe_result = recipe_script.run(api, properties)
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts\slave\.recipe_deps\recipe_engine\recipe_engine\loader.py", line 81, in run
    self.run_steps, properties, self.PROPERTIES, api=api)
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts\slave\.recipe_deps\recipe_engine\recipe_engine\loader.py", line 580, in invoke_with_properties
    **additional_args)
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts\slave\.recipe_deps\recipe_engine\recipe_engine\loader.py", line 541, in _invoke_with_properties
    return callable_obj(*props, **additional_args)
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts/slave\recipes\findit/chromium/test.py", line 179, in RunSteps
    revision, tests_to_run, use_analyze))
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts\slave\.recipe_deps\recipe_engine\recipe_engine\recipe_api.py", line 578, in _inner
    return func(*a, **kw)
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts/slave\recipe_modules\findit\api.py", line 228, in compile_and_test_at_revision
    api, actual_tests_to_run, suffix=str(revision))
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts\slave\.recipe_deps\recipe_engine\recipe_engine\recipe_api.py", line 578, in _inner
    return func(*a, **kw)
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts/slave\recipe_modules\test_utils\api.py", line 89, in run_tests
    t.pre_run(caller_api, suffix)
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts/slave\recipe_modules\chromium_tests\steps.py", line 1768, in pre_run
    return self._test.pre_run(api, suffix)
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts/slave\recipe_modules\chromium_tests\steps.py", line 1153, in pre_run
    return api.swarming.trigger_task(self._tasks[suffix])
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts\slave\.recipe_deps\recipe_engine\recipe_engine\recipe_api.py", line 578, in _inner
    return func(*a, **kw)
  File "C:\b\rr\tmpxetrzq\rw\checkout\scripts/slave\recipe_modules\swarming\api.py", line 561, in trigger_task
    'Triggered same task twice: %s' % task.task_name)
AssertionError: Triggered same task twice: blink_platform_unittests (4dbfdb063d396295597734d850b8f41c20aa50f1)/Windows-7-SP1/539da50d66/win_chromium_variable_webkit_win7_builder_x64/78