system_health.common_desktop/browse:media:tumblr flaky on chromium.perf/Win 7 Perf

Builders failed on: 
- Win 7 Perf: 
  https://build.chromium.org/p/chromium.perf/builders/Win%207%20Perf

5 of the last 12 builds have failed for browse:media:tumblr

https://chromium-swarm.appspot.com/task?id=391eb6b6a48a1e10&refresh=10&show_raw=1
  File "c:\b\s\w\ir\third_party\catapult\telemetry\telemetry\internal\backends\chrome_inspector\inspector_backend.py", line 518, in _EvaluateJavaScript
    return self._runtime.Evaluate(expression, context_id, timeout)
  File "c:\b\s\w\ir\third_party\catapult\telemetry\telemetry\internal\backends\chrome_inspector\inspector_runtime.py", line 53, in Evaluate
    description=details.get('exception', {}).get('description'))
EvaluateException: UncaughtError:
Error: Cannot find element: using selector "#tumblr_lightbox_center_image"
    at callback (<anonymous>:7:19)
    at <anonymous>:13:16
    at <anonymous>:14:9

https://console.developers.google.com/m/cloudstorage/b/chrome-telemetry-output/o/profiler-file-id_54-2017-10-10_07-14-3217011.png
Not sure if "You'll never be bored again. Sign up for Tumbler" is usually there, but it is in all these failing cases

I'll go ahead and disable browse:media:tumbler for win 7 perf