Notes to self:
* crash_reporter special casing for --mus should go away permanently
* --mash handling should go away temporarily, but come back when service manager moves into ash
* If crashpad ships on Chrome OS before mash launches --mash might not be relevant
* Need to check if chrome's crash reporter client interface is installed early enough to catch early service startup crashes

Filed  issue 772098  for bring-down-the-world being broken.

Yes, crash reporting needs to be fixed. Right now both the browser process crash reporter and the OS-level crash reporter are both trying to handle --mash processes. There can be only one. :-)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/35e3f440086066ce73c119f11212f448991cd162

commit 35e3f440086066ce73c119f11212f448991cd162
Author: James Cook <jamescook@chromium.org>
Date: Fri Oct 20 17:44:26 2017

crash: Update flag to detect chrome mash crashes

Use --mash-service-process to identify the processes that need
crash reporter to handle their dumping, rather than the old
--mash and --mus.

Chrome-side change is crrev.com/c/729064

BUG= chromium:771801 
TEST=updated unit tests, manual test on device
Change-Id: Ia90228d106ec99423c11178e8522677f40308357
Reviewed-on: https://chromium-review.googlesource.com/729215
Commit-Ready: James Cook <jamescook@chromium.org>
Tested-by: James Cook <jamescook@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/35e3f440086066ce73c119f11212f448991cd162/crash-reporter/user_collector.h
[modify] https://crrev.com/35e3f440086066ce73c119f11212f448991cd162/crash-reporter/user_collector_test.cc
[modify] https://crrev.com/35e3f440086066ce73c119f11212f448991cd162/crash-reporter/user_collector.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e91ab17a3dd03cb21ec0b120b64764aa15c535f4

commit e91ab17a3dd03cb21ec0b120b64764aa15c535f4
Author: James Cook <jamescook@chromium.org>
Date: Fri Oct 20 18:03:01 2017

cros: Use OS-level crash reporter for mash service process crashes

Disable breakpad in-process stack dumping for mash service processes
by removing the --enable-crash-reporter switch when they launch. The
OS-level crash_reporter has a matching change that triggers crash
dumping for those processes. Also, exit the parent browser / service
manager process to avoid triggering a crash report for that process.

Bug:  771801 
Test: added ChromeContentBrowserClientMashTest.CrashReporter
Change-Id: Id7847f72ed4b6973ab924bafb4c67d7a333cf302
Reviewed-on: https://chromium-review.googlesource.com/729064
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510488}
[modify] https://crrev.com/e91ab17a3dd03cb21ec0b120b64764aa15c535f4/chrome/browser/chrome_content_browser_client.cc
[add] https://crrev.com/e91ab17a3dd03cb21ec0b120b64764aa15c535f4/chrome/browser/chrome_content_browser_client_browsertest_chromeos.cc
[modify] https://crrev.com/e91ab17a3dd03cb21ec0b120b64764aa15c535f4/chrome/common/chrome_switches.cc
[modify] https://crrev.com/e91ab17a3dd03cb21ec0b120b64764aa15c535f4/chrome/common/chrome_switches.h
[modify] https://crrev.com/e91ab17a3dd03cb21ec0b120b64764aa15c535f4/chrome/test/BUILD.gn
[modify] https://crrev.com/e91ab17a3dd03cb21ec0b120b64764aa15c535f4/content/browser/service_manager/service_manager_context.cc
[modify] https://crrev.com/e91ab17a3dd03cb21ec0b120b64764aa15c535f4/services/service_manager/embedder/main.cc
[modify] https://crrev.com/e91ab17a3dd03cb21ec0b120b64764aa15c535f4/testing/buildbot/filters/mash.browser_tests.filter
[modify] https://crrev.com/e91ab17a3dd03cb21ec0b120b64764aa15c535f4/testing/buildbot/filters/mojo.fyi.browser_tests.filter