Exit WebContent immediately when either browser-side IPC peer
disconnects. Plumb Unix process exit status through LibWebView so the
browser process can tell clean owner-driven shutdown apart from renderer
crashes.
This keeps nonzero exits and signal deaths reported as crashes, while
letting status 0 exits disappear without making test-web report the page
as crashed.
Now that we detect and handle child processes exiting, we should see
less "Trying to post_message during IPC shutdown" VERIFY failures that
crash the UI process.
Co-authored-by: Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
There is no direct equivalent to SIGCHILD on Windows. The closest we
can get is monitoring a specific process, given a known pid. On Unix
there is no single solution to be able to do that in LibCore's
EventLoopImplementationUnix. For Linux there's a SYS_pidfd_open syscall
that can integrate into poll(), but on macOS a kqueue would be needed.
Given macOS uses EventLoopImplementationUnix for the headless view
implementation, we currently can't create a fully cross-platform
abstaction at the Event Loop level to match what Windows needs to do.
ProcessMonitor's purpose is to abstract away the Unix vs Windows
behaviour avoiding more inlined ifdef soup in ProcessManager.
