I don't understand this bug. I loaded as many of the builds as I could (200 builds), and the bot has been error or red the whole time. What made you think this particular range is problematic?

Printout of the page I see

Deleted: Buildbot_ Android Nexus5 Perf (1).pdf 1.3 MB

Buildbot_ Android Nexus5 Perf (1).pdf 1.3 MB Download

This is continuing to fail on Android Nexus5 Perf (1), Please investigate. 

Link to builder:
https://uberchromegw.corp.google.com/i/chromium.perf/builders/Android%20Nexus5%20Perf%20%281%29?numbuilds=200 


Link to log: https://uberchromegw.corp.google.com/i/chromium.perf/builders/Android%20Nexus5%20Perf%20%281%29/builds/4423/steps/blink_style.key_mobile_sites.reference/logs/stdio


Stack trace: 

Traceback (most recent call last):
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/story_runner.py", line 86, in _RunStoryAndProcessErrorIfNeeded
    state.RunStory(results)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/common/py_trace_event/py_trace_event/trace_event_impl/decorators.py", line 52, in traced_function
    return func(*args, **kwargs)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/page/shared_page_state.py", line 310, in RunStory
    self._current_page.Run(self)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/page/__init__.py", line 105, in Run
    shared_state.page_test.RunNavigateSteps(self, current_tab)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/common/py_trace_event/py_trace_event/trace_event_impl/decorators.py", line 75, in traced_function
    return func(*args, **kwargs)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/page/legacy_page_test.py", line 195, in RunNavigateSteps
    page.RunNavigateSteps(action_runner)
  File "/b/rr/tmpKmNEJq/w/src/tools/perf/page_sets/key_mobile_sites_pages.py", line 29, in RunNavigateSteps
    super(CapitolVolkswagenPage, self).RunNavigateSteps(action_runner)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/page/__init__.py", line 114, in RunNavigateSteps
    url, script_to_evaluate_on_commit=self.script_to_evaluate_on_commit)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/actions/action_runner.py", line 155, in Navigate
    timeout_in_seconds=timeout_in_seconds))
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/actions/action_runner.py", line 48, in _RunAction
    action.RunAction(self._tab)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/common/py_trace_event/py_trace_event/trace_event_impl/decorators.py", line 75, in traced_function
    return func(*args, **kwargs)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/actions/navigate.py", line 30, in RunAction
    tab.WaitForFrameToBeDisplayed()
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 98, in WaitForFrameToBeDisplayed
    timeout)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 123, in WaitForJavaScriptExpression
    util.WaitFor(IsJavaScriptExpressionTrue, timeout)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/core/util.py", line 86, in WaitFor
    res = condition()
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 116, in IsJavaScriptExpressionTrue
    return bool(self.EvaluateJavaScript(expr))
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 187, in EvaluateJavaScript
    expr, context_id=None, timeout=timeout)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 215, in EvaluateJavaScriptInContext
    expr, context_id=context_id, timeout=timeout)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/common/py_trace_event/py_trace_event/trace_event_impl/decorators.py", line 75, in traced_function
    return func(*args, **kwargs)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py", line 37, in inner
    inspector_backend._ConvertExceptionFromInspectorWebsocket(e)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/common/py_trace_event/py_trace_event/trace_event_impl/decorators.py", line 75, in traced_function
    return func(*args, **kwargs)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py", line 34, in inner
    return func(inspector_backend, *args, **kwargs)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py", line 208, in EvaluateJavaScript
    return self._runtime.Evaluate(expr, context_id, timeout)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_runtime.py", line 45, in Evaluate
    res = self._inspector_websocket.SyncRequest(request, timeout)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_websocket.py", line 110, in SyncRequest
    res = self._Receive(timeout)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_websocket.py", line 149, in _Receive
    data = self._socket.recv()
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/third_party/websocket-client/websocket.py", line 596, in recv
    opcode, data = self.recv_data()
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/third_party/websocket-client/websocket.py", line 606, in recv_data
    frame = self.recv_frame()
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/third_party/websocket-client/websocket.py", line 637, in recv_frame
    self._frame_header = self._recv_strict(2)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/third_party/websocket-client/websocket.py", line 746, in _recv_strict
    bytes = self._recv(shortage)
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/third_party/websocket-client/websocket.py", line 739, in _recv
  File "/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/third_party/websocket-client/websocket.py", line 739, in _recv
    raise WebSocketConnectionClosedException()
DevtoolsTargetCrashException: Devtools target crashed
********************************************************************************
(/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py:394 _ConvertExceptionFromInspectorWebsocket) Original exception:

********************************************************************************
(/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py:415 _AddDebuggingInformation) Received a socket error in the browser connection and the tab no longer exists. The tab probably crashed.
********************************************************************************
(/b/rr/tmpKmNEJq/w/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py:416 _AddDebuggingInformation) Debugger url: ws://127.0.0.1:43276/devtools/page/0
Found Minidump: True

Presumably someone landed a change that broke this, but it certainly wasn't me. If we don't know what the actual regression range is, perhaps someone could bisect this.

Please see #4.

Seems to have resolved itself now.