On "Mac FYI Experimental Retina Release (AMD)", lately, we've been seeing some failing test runs. Telemetry seems to attempt to bring up the browser 3 times, but applescript fails to connect (the -609 error):

81:89: execution error: Chromium got an error: Connection is invalid. (-609)
(WARNING) 2018-09-14 10:33:16,368 gpu_integration_test.StartBrowser:99  Browser start failed (attempt 2 of 3)
(INFO) 2018-09-14 10:33:16,368 browser.Close:208  Closing browser (pid=529) ...
(WARNING) 2018-09-14 10:33:22,077 desktop_browser_backend.Close:574  Failed to gracefully shutdown.
(WARNING) 2018-09-14 10:33:22,077 desktop_browser_backend.Close:578  Proceed to kill the browser.
(INFO) 2018-09-14 10:33:22,079 browser.Close:221  Browser is closed.

the relevant applescript is here:
https://cs.chromium.org/chromium/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome/desktop_browser_backend.py?l=254&rcl=9f36d9f788130761c3611060bc7a104772761d15

I want to add a little bit of logging in desktop_browser_backend.Close so we can try to see whether the process is totally dead, or not, here:
https://cs.chromium.org/chromium/src/third_party/catapult/telemetry/telemetry/internal/backends/chrome/desktop_browser_backend.py?l=579&rcl=9f36d9f788130761c3611060bc7a104772761d15