Every now and then this benchmark times out on:
https://luci-milo.appspot.com/buildbot/chromium.perf/Mac%20Retina%20Perf/

From latest 20 builds ('T' is timeout, '-' is success):
mac-retina common   T--T-T--T-TT-TT---T-

Example recent build:
https://luci-milo.appspot.com/buildbot/chromium.perf/Mac%20Retina%20Perf/616

The step says:
"shard #0 timed out, took too much time to complete"

Interestingly the test only ran for 1 hour 39 minutes, and the log shows that the benchmark run was actually interrupted with an exception:

(ERROR) 2017-05-03 18:41:59,280 battor_wrapper._FlashBattOr:158  Git hash returned from BattOr was not as expected: [0503/184159.279148:FATAL:battor_agent_bin.cc(89)] Fatal error when communicating with the BattOr: TIMEOUT
Traceback (most recent call last):
  File "/b/s/w/ir/third_party/catapult/common/battor/battor/battor_wrapper.py", line 145, in _FlashBattOr
    device_git_hash = self.GetFirmwareGitHash()
  File "/b/s/w/ir/third_party/catapult/common/battor/battor/battor_wrapper.py", line 373, in GetFirmwareGitHash
    int(self._git_hash, 16)
ValueError: invalid literal for int() with base 16: '[0503/184159.279148:FATAL:battor_agent_bin.cc(89)] Fatal error when communicating with the BattOr: TIMEOUT'
(WARNING) 2017-05-03 18:41:59,281 shared_page_state.DumpStateUponFailure:131  Cannot dump browser state: No browser.
Traceback (most recent call last):
  File "/b/s/w/ir/third_party/catapult/telemetry/telemetry/internal/story_runner.py", line 80, in _RunStoryAndProcessErrorIfNeeded
    test.WillRunStory(state.platform)
  File "/b/s/w/ir/third_party/catapult/telemetry/telemetry/web_perf/timeline_based_measurement.py", line 285, in WillRunStory
    platform.tracing_controller.StartTracing(self._tbm_options.config)
  File "/b/s/w/ir/third_party/catapult/telemetry/telemetry/core/tracing_controller.py", line 43, in StartTracing
    self._tracing_controller_backend.StartTracing(tracing_config, timeout)
  File "/b/s/w/ir/third_party/catapult/telemetry/telemetry/internal/platform/tracing_controller_backend.py", line 91, in StartTracing
    started = agent.StartAgentTracing(config, timeout)
  File "/b/s/w/ir/third_party/catapult/telemetry/telemetry/internal/platform/tracing_agent/battor_tracing_agent.py", line 73, in StartAgentTracing
    self._battor.StartTracing()
  File "/b/s/w/ir/third_party/catapult/common/battor/battor/battor_wrapper.py", line 216, in StartTracing
    self._SendBattOrCommand(self._START_TRACING_CMD)
  File "/b/s/w/ir/third_party/catapult/common/battor/battor/battor_wrapper.py", line 326, in _SendBattOrCommand
    status = self._SendBattOrCommandImpl(cmd)
  File "/b/s/w/ir/third_party/catapult/common/battor/battor/battor_wrapper.py", line 321, in _SendBattOrCommandImpl
    self._battor_shell.stdin.write('%s\n' % cmd)
IOError: [Errno 32] Broken pipe

https://luci-logdog.appspot.com/v/?s=chrome%2Fbb%2Fchromium.perf%2FMac_Retina_Perf%2F616%2F%2B%2Frecipes%2Fsteps%2Fsystem_health.common_desktop_on_Intel_GPU_on_Mac_on_Mac-10.11%2F0%2Fstdout

What is the timeout for this step? Was it really a shard timing out?