The GPU tests seem to have become flaky recently because of problems starting the browser reliably. Here are a couple of builds on Mac and Linux which demonstrate the problem:

https://build.chromium.org/p/chromium.gpu.fyi/builders/Mac%20Retina%20Release/builds/5617
Failed:
GpuRasterization.BlueBox
GpuRasterization.ConcavePaths

https://build.chromium.org/p/chromium.gpu.fyi/builders/Mac%20Retina%20Release/builds/5615
Failed shard #9:
https://chromium-swarm.appspot.com/user/task/300805d55514a210

https://build.chromium.org/p/chromium.gpu.fyi/builders/Linux%20Debug%20%28New%20Intel%29/builds/2842
Failed:
ContextLost.WebGLContextLostFromLoseContextExtension

Failure mode:
[ RUN      ] ContextLost.WebGLContextLostFromLoseContextExtension
...
(WARNING) 2016-07-15 07:48:32,391 desktop_browser_backend._GetAllCrashpadMinidumps:346  No path to crashpad_database_util found
(INFO) 2016-07-15 07:48:32,391 desktop_browser_backend._GetMostRecentMinidump:414  No minidump found via crashpad_database_util
Can't get standard output with --show-stdout
(WARNING) 2016-07-15 07:48:37,474 desktop_browser_backend.Close:586  Failed to gracefully shutdown.
(WARNING) 2016-07-15 07:48:37,474 desktop_browser_backend.Close:590  Proceed to kill the browser.
(ERROR) 2016-07-15 07:48:37,477 browser.__init__:62  Failure while starting browser backend.
Traceback (most recent call last):
  File "/tmp/isolated_runYKtdNK/third_party/catapult/telemetry/telemetry/internal/browser/browser.py", line 55, in __init__
    self._browser_backend.Start()
  File "/tmp/isolated_runYKtdNK/third_party/catapult/telemetry/telemetry/internal/backends/chrome/desktop_browser_backend.py", line 291, in Start
    self._WaitForBrowserToComeUp()
  File "/tmp/isolated_runYKtdNK/third_party/catapult/telemetry/telemetry/internal/backends/chrome/chrome_browser_backend.py", line 174, in _WaitForBrowserToComeUp
    raise exceptions.BrowserConnectionGoneException(self.browser, e)
BrowserConnectionGoneException: Timed out while waiting 60s for HasBrowserFinishedLaunching.
Found Minidump: False
Stack Trace:
********************************************************************************
	No crash dump found.
********************************************************************************
Standard output:
********************************************************************************
********************************************************************************
(WARNING) 2016-07-15 07:48:37,478 shared_page_state.DumpStateUponFailure:138  Cannot dump browser state: No browser.
(WARNING) 2016-07-15 07:48:37,478 shared_page_state.DumpStateUponFailure:144  Taking screenshots upon failures disabled.
(INFO) 2016-07-15 07:48:37,482 cmd_helper._ValidateAndLogCommand:153  [host]> /tmp/isolated_runYKtdNK/third_party/catapult/devil/bin/deps/linux2/x86_64/bin/adb devices
Traceback (most recent call last):
  File "/tmp/isolated_runYKtdNK/third_party/catapult/telemetry/telemetry/internal/story_runner.py", line 78, in _RunStoryAndProcessErrorIfNeeded
    state.WillRunStory(story)
  File "/tmp/isolated_runYKtdNK/third_party/catapult/telemetry/telemetry/page/shared_page_state.py", line 242, in WillRunStory
    self._StartBrowser(page)
  File "/tmp/isolated_runYKtdNK/third_party/catapult/telemetry/telemetry/page/shared_page_state.py", line 202, in _StartBrowser
    self._browser = self._possible_browser.Create(self._finder_options)
  File "/tmp/isolated_runYKtdNK/third_party/catapult/telemetry/telemetry/internal/backends/chrome/desktop_browser_finder.py", line 68, in Create
    browser_backend, self._platform_backend, self._credentials_path)
  File "/tmp/isolated_runYKtdNK/third_party/catapult/telemetry/telemetry/internal/browser/browser.py", line 55, in __init__
    self._browser_backend.Start()
  File "/tmp/isolated_runYKtdNK/third_party/catapult/telemetry/telemetry/internal/backends/chrome/desktop_browser_backend.py", line 291, in Start
    self._WaitForBrowserToComeUp()
  File "/tmp/isolated_runYKtdNK/third_party/catapult/telemetry/telemetry/internal/backends/chrome/chrome_browser_backend.py", line 174, in _WaitForBrowserToComeUp
    raise exceptions.BrowserConnectionGoneException(self.browser, e)
BrowserConnectionGoneException: Timed out while waiting 60s for HasBrowserFinishedLaunching.
Found Minidump: False
Stack Trace:
********************************************************************************
	No crash dump found.
********************************************************************************
Standard output:
********************************************************************************
********************************************************************************

[  FAILED  ] ContextLost.WebGLContextLostFromLoseContextExtension (69295 ms)

I'm not sure whether this is happening on the waterfalls -- haven't checked, but haven't received widespread notices from chromium-try-flakes -- but it is new behavior, and serious, that the browser doesn't launch reliably.

 

Deleted: stdout-gpu-rasterization-mac.txt 33.5 KB

stdout-gpu-rasterization-mac.txt 33.5 KB View Download

Deleted: stdout-webgl2-conformance-failed-shard.txt 7.6 KB

stdout-webgl2-conformance-failed-shard.txt 7.6 KB View Download

Deleted: stdout-context-lost-tests-linux.txt 109 KB

stdout-context-lost-tests-linux.txt 109 KB View Download