Stack trace, looks like a problem with tracing.

Traceback (most recent call last):
  File "/b/swarming/w/ir/third_party/catapult/telemetry/telemetry/internal/story_runner.py", line 125, in _RunStoryAndProcessErrorIfNeeded
    test.Measure(state.platform, results)
  File "/b/swarming/w/ir/third_party/catapult/telemetry/telemetry/web_perf/timeline_based_measurement.py", line 261, in Measure
    trace_result, _ = platform.tracing_controller.StopTracing()
  File "/b/swarming/w/ir/third_party/catapult/telemetry/telemetry/core/tracing_controller.py", line 53, in StopTracing
    return self._tracing_controller_backend.StopTracing()
  File "/b/swarming/w/ir/third_party/catapult/telemetry/telemetry/internal/platform/tracing_controller_backend.py", line 161, in StopTracing
    '\n'.join(raised_exception_messages))
TracingException: Exceptions raised when trying to stop tracing:
Traceback (most recent call last):
  File "/b/swarming/w/ir/third_party/catapult/telemetry/telemetry/internal/platform/tracing_controller_backend.py", line 149, in StopTracing
    agent.CollectAgentTraceData(builder)
  File "/b/swarming/w/ir/third_party/catapult/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py", line 250, in CollectAgentTraceData
    '\n'.join(raised_exception_messages))
ChromeTracingStoppedError: Exceptions raised when trying to collect Chrome devtool tracing:
Error when collecting Chrome tracing on devtools at port localabstract:chrome_devtools_remote:
Traceback (most recent call last):
  File "/b/swarming/w/ir/third_party/catapult/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py", line 239, in CollectAgentTraceData
    client.CollectChromeTracingData(trace_data_builder)
  File "/b/swarming/w/ir/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/devtools_client_backend.py", line 462, in CollectChromeTracingData
    self._tracing_backend.CollectTraceData(trace_data_builder, timeout)
  File "/b/swarming/w/ir/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/tracing_backend.py", line 231, in CollectTraceData
    self._CollectTracingData(trace_data_builder, timeout)
  File "/b/swarming/w/ir/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/tracing_backend.py", line 269, in _CollectTracingData
    'the timeout amount.' % elapsed_time)
TracingTimeoutException: Only received partial trace data due to timeout after 60.0580079556 seconds. If the trace data is big, you may want to increase the timeout amount.

Link to the most recent log: https://chromium-swarm.appspot.com/task?id=3bd5334f15bf0810&refresh=10&show_raw=1

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/25045a69100f22c263fbde5de793d189a75d7e28

commit 25045a69100f22c263fbde5de793d189a75d7e28
Author: Emily Hanley <eyaich@google.com>
Date: Fri Feb 23 16:14:00 2018

Disabling v8.browsing_mobile/browse:news:cnn on Nexus5.

TBR=charliea@chromium.org

NOTRY=true

Bug: 815175
Change-Id: I845756bd9ead74657ccc80a8a3568dc615ed3bb6
Reviewed-on: https://chromium-review.googlesource.com/934627
Commit-Queue: Emily Hanley <eyaich@chromium.org>
Reviewed-by: Emily Hanley <eyaich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#538794}
[modify] https://crrev.com/25045a69100f22c263fbde5de793d189a75d7e28/tools/perf/expectations.config