We are seeing system_health.memory_desktop failing on several mac bots ( including the swarmed mac bots):

 Mac 10.10 Perf (3):
https://uberchromegw.corp.google.com/i/chromium.perf/builders/Mac%2010.10%20Perf%20%283%29/builds/4270

Mac Retina Perf (3): 
https://uberchromegw.corp.google.com/i/chromium.perf/builders/Mac%20Retina%20Perf%20%283%29/builds/4094

Mac HDD Perf(3): 
https://uberchromegw.corp.google.com/i/chromium.perf/builders/Mac%20HDD%20Perf%20%283%29/builds/2570

Mac Pro 10.11 Perf:
https://chromium-swarm.appspot.com/user/task/32578aba6b181810

Mac Air 10.11 Perf:
https://chromium-swarm.appspot.com/user/task/32572497defaff10

I am also seeing the same stack trace for system_health.common_desktop for the swarmed mac bots: 

Mac Pro 10.11 Perf:
https://chromium-swarm.appspot.com/user/task/32578aaf2efc9e10

Mac Air 10.11 Perf:
https://chromium-swarm.appspot.com/user/task/32572489832bac10

Snippet of stack trace: 
INFO:root:Minidump found: /b/s/w/itMse6iM/tmpGfnJrK/completed/385d256c-948c-4584-b439-f68083f7e85f.dmp
INFO:py_utils.cloud_storage:Downloading gs://chromium-telemetry/binary_dependencies/minidump_stackwalk_76c5983fc9e9316a9d4251ba3e68b955c4fc9bf3 to /b/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/bin/mac/x86_64/minidump_stackwalk
INFO:root:Dumping breakpad symbols.
INFO:py_utils.cloud_storage:Downloading gs://chromium-telemetry/binary_dependencies/minidump_dump_c39bd7a3b9fa6279893b2d759045699d79ce4dcb to /b/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/bin/mac/x86_64/minidump_dump
INFO:root:Found crashpad_database_util
[1107/064856:WARNING:crash_report_database_mac.mm(697)] Failed to read report metadata for /b/s/w/itMse6iM/tmpGfnJrK/completed/385d256c-948c-4584-b439-f68083f7e85f.dmp.stripped
INFO:root:*************** BROWSER STANDARD OUTPUT ***************
INFO:root:
INFO:root:*********** END OF BROWSER STANDARD OUTPUT ************
INFO:root:********************* BROWSER LOG *********************
INFO:root:No log file
INFO:root:***************** END OF BROWSER LOG ******************
Traceback (most recent call last):
  File "/b/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/story_runner.py", line 87, in _RunStoryAndProcessErrorIfNeeded
    state.RunStory(results)
  File "/b/s/w/irLRJx3H/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/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/page/shared_page_state.py", line 299, in RunStory
    self._current_page.Run(self)
  File "/b/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/page/__init__.py", line 109, in Run
    self.RunPageInteractions(action_runner)
  File "/b/s/w/irLRJx3H/tools/perf/page_sets/system_health/system_health_story.py", line 112, in RunPageInteractions
    self._DidLoadDocument(action_runner)
  File "/b/s/w/irLRJx3H/tools/perf/page_sets/system_health/browsing_stories.py", line 71, in _DidLoadDocument
    self._NavigateToItem(action_runner, i)
  File "/b/s/w/irLRJx3H/tools/perf/page_sets/system_health/browsing_stories.py", line 33, in _NavigateToItem
    action_runner.ScrollPageToElement(element_function=item_selector)
  File "/b/s/w/irLRJx3H/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/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/actions/action_runner.py", line 429, in ScrollPageToElement
    speed_in_pixels_per_second=speed_in_pixels_per_second))
  File "/b/s/w/irLRJx3H/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/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/actions/action_runner.py", line 55, in _RunAction
    action.RunAction(self._tab)
  File "/b/s/w/irLRJx3H/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/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/actions/scroll_to_element.py", line 65, in RunAction
    self._scroller.RunAction(tab)
  File "/b/s/w/irLRJx3H/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/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/actions/scroll.py", line 106, in RunAction
    tab.WaitForJavaScriptExpression('window.__scrollActionDone', 60)
  File "/b/s/w/irLRJx3H/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/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 129, in WaitForJavaScriptExpression
    py_utils.WaitFor(IsJavaScriptExpressionTrue, timeout)
  File "/b/s/w/irLRJx3H/third_party/catapult/common/py_utils/py_utils/__init__.py", line 120, in WaitFor
    res = condition()
  File "/b/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 122, in IsJavaScriptExpressionTrue
    return bool(self.EvaluateJavaScript(expr))
  File "/b/s/w/irLRJx3H/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/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 193, in EvaluateJavaScript
    expr, context_id=None, timeout=timeout)
  File "/b/s/w/irLRJx3H/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/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/browser/web_contents.py", line 221, in EvaluateJavaScriptInContext
    expr, context_id=context_id, timeout=timeout)
  File "/b/s/w/irLRJx3H/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/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py", line 39, in inner
    inspector_backend._ConvertExceptionFromInspectorWebsocket(e)
  File "/b/s/w/irLRJx3H/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/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py", line 36, in inner
    return func(inspector_backend, *args, **kwargs)
  File "/b/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_backend.py", line 211, in EvaluateJavaScript
    return self._runtime.Evaluate(expr, context_id, timeout)
  File "/b/s/w/irLRJx3H/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/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_websocket.py", line 110, in SyncRequest
    res = self._Receive(timeout)
  File "/b/s/w/irLRJx3H/third_party/catapult/telemetry/telemetry/internal/backends/chrome_inspector/inspector_websocket.py", line 149, in _Receive
    data = self._socket.recv()
  File "/b/s/w/irLRJx3H/third_party/catapult/telemetry/third_party/websocket-client/websocket.py", line 596, in recv
    opcode, data = self.recv_data()
  File "/b/s/w/irLRJx3H/third_party/catapult/telemetry/third_party/websocket-client/websocket.py", line 606, in recv_data
    frame = self.recv_frame()
  File "/b/s/w/irLRJx3H/third_party/catapult/telemetry/third_party/websocket-client/websocket.py", line 637, in recv_frame
    self._frame_header = self._recv_strict(2)
  File "/b/s/w/irLRJx3H/third_party/catapult/telemetry/third_party/websocket-client/websocket.py", line 746, in _recv_strict
    bytes = self._recv(shortage)
  File "/b/s/w/irLRJx3H/third_party/catapult/telemetry/third_party/websocket-client/websocket.py", line 739, in _recv
    raise WebSocketConnectionClosedException()
DevtoolsTargetCrashException: <unprintable DevtoolsTargetCrashException object>