android: Deal with child process termination before launch has concluded

If BrowserChildProcessHostImpl is deleted before a pending child process
launch has finished, child process disconnection can be notified without
a valid process id for the child process. This patch changes the child
exit observer to deal with this case. By code inspection both clients of
this class (AwBrowserTerminator, ChildProcessCrashObserver) can already
deal with notifications without a valid process id.

Bug: 863341
Change-Id: I4237b1df68072263916e31dd23684519b6810bd4
Reviewed-on: https://chromium-review.googlesource.com/c/1455944
Commit-Queue: Sami Kyöstilä <skyostil@chromium.org>
Commit-Queue: Peter Wen <wnwen@chromium.org>
Auto-Submit: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629587}
2 files changed