This message type allows the browser to determine the handler's process
ID to be used with `prctl(PR_SET_PTRACER, ...)`.
Bug: crashpad:284
Change-Id: I2664f3e8aee269b159de9074e389397346c808f0
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/1577704
Reviewed-by: Mark Mentovai <mark@chromium.org>