Many timeouts on memory_top_10_mobile. It's across many different tests, so I don't think it's a problem in a particular benchmark. The errors are like:


Exception raised when cleaning story run: 

Traceback (most recent call last):
  _RunStoryAndProcessErrorIfNeeded at /b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/internal/story_runner.py:159
    test.DidRunStory(state.platform, results)
  DidRunStory at /b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/web_perf/timeline_based_measurement.py:296
    trace_result, _ = platform.tracing_controller.StopTracing()
  StopTracing at /b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/core/tracing_controller.py:53
    return self._tracing_controller_backend.StopTracing()
  StopTracing at /b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/internal/platform/tracing_controller_backend.py:157
    '\n'.join(raised_exception_messages))
TracingException: Exceptions raised when trying to stop tracing:
Traceback (most recent call last):
  File "/b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/internal/platform/tracing_controller_backend.py", line 145, in StopTracing
    agent.CollectAgentTraceData(builder)
  File "/b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py", line 248, 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:webview_devtools_remote_7350:
Traceback (most recent call last):
  File "/b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py", line 237, in CollectAgentTraceData
    client.CollectChromeTracingData(trace_data_builder)
  File "/b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/devtools_client_backend.py", line 489, in CollectChromeTracingData
    self._tracing_backend.CollectTraceData(trace_data_builder, timeout)
  File "/b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/tracing_backend.py", line 237, in CollectTraceData
    self._CollectTracingData(trace_data_builder, timeout)
  File "/b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/tracing_backend.py", line 279, in _CollectTracingData
    'the timeout amount.' % elapsed_time)
TracingTimeoutException: Only received partial trace data due to timeout after 120.086297035 seconds. If the trace data is big, you may want to increase the timeout amount.

Locals:
  agent                     : <telemetry.internal.platform.tracing_controller_backend.TracingControllerBackend object at 0x7efd83e4c150>
  builder                   : <tracing.trace_data.trace_data.TraceDataBuilder object at 0x7efd827bf6d0>
  raised_exception_messages : ['Traceback (most recent call last):\n  File "/b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/internal/platform/tracing_controller_backend.py", line 145, in StopTracing\n    agent.CollectAgentTraceData(builder)\n  File "/b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py", line 248, in CollectAgentTraceData\n    \'\\n\'.join(raised_exception_messages))\nChromeTracing ... d.py", line 237, in CollectTraceData\n    self._CollectTracingData(trace_data_builder, timeout)\n  File "/b/build/slave/health-plan-webview-phone/build/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/tracing_backend.py", line 279, in _CollectTracingData\n    \'the timeout amount.\' % elapsed_time)\nTracingTimeoutException: Only received partial trace data due to timeout after 120.086297035 seconds. If the trace data is big, you may want to increase the timeout amount.\n\n'] (truncated)


Looking at successful runs, the trace processing time is just a couple of seconds. So something is actually going wrong rather than just gradually slowing down.