blink_perf.pywebsocket failing on 9 builders

Type: build-failure

Builders failed on: 
- Android Nexus5 Perf (3): 
  https://build.chromium.org/p/chromium.perf/builders/Android%20Nexus5%20Perf%20%283%29
- Android Nexus5X Perf (3): 
  https://build.chromium.org/p/chromium.perf/builders/Android%20Nexus5X%20Perf%20%283%29
- Android Nexus5X WebView Perf (3): 
  https://build.chromium.org/p/chromium.perf/builders/Android%20Nexus5X%20WebView%20Perf%20%283%29
- Android Nexus6 Perf (3): 
  https://build.chromium.org/p/chromium.perf/builders/Android%20Nexus6%20Perf%20%283%29
- Android Nexus6 WebView Perf (3): 
  https://build.chromium.org/p/chromium.perf/builders/Android%20Nexus6%20WebView%20Perf%20%283%29
- Android Nexus7v2 Perf (3): 
  https://build.chromium.org/p/chromium.perf/builders/Android%20Nexus7v2%20Perf%20%283%29
- Android Nexus9 Perf (3): 
  https://build.chromium.org/p/chromium.perf/builders/Android%20Nexus9%20Perf%20%283%29
- Linux Perf (1): 
  https://build.chromium.org/p/chromium.perf/builders/Linux%20Perf%20%281%29
- Mac 10.11 Perf (1): 
  https://build.chromium.org/p/chromium.perf/builders/Mac%2010.11%20Perf%20%281%29


Traceback (most recent call last):
  _RunStoryAndProcessErrorIfNeeded at /b/c/b/Linux_Perf__1_/src/third_party/catapult/telemetry/telemetry/internal/story_runner.py:104
    state.DidRunStory(results)
  traced_function at /b/c/b/Linux_Perf__1_/src/third_party/catapult/common/py_trace_event/py_trace_event/trace_event_impl/decorators.py:52
    return func(*args, **kwargs)
  DidRunStory at /b/c/b/Linux_Perf__1_/src/third_party/catapult/telemetry/telemetry/page/shared_page_state.py:163
    self._current_tab.Close()
  Close at /b/c/b/Linux_Perf__1_/src/third_party/catapult/telemetry/telemetry/internal/browser/tab.py:100
    self._tab_list_backend.CloseTab(self.id)
  CloseTab at /b/c/b/Linux_Perf__1_/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome/tab_list_backend.py:66
    util.WaitFor(lambda: tab_id not in self.IterContextIds(), timeout=5)
  WaitFor at /b/c/b/Linux_Perf__1_/src/third_party/catapult/telemetry/telemetry/core/util.py:94
    (timeout, GetConditionString()))
TimeoutException: Timed out while waiting 5s for util.WaitFor(lambda: tab_id not in self.IterContextIds(), timeout=5).