createPidFile(dir, content) can be used to create the pid file for
the current process with the given content in the dir.
listPidFiles(dir) can be used to list pid files in the given directory.
Both functions will purge stale pid files from the given directory.
The implementation operates under the assumption that there is only
a small number of processes using pid files running at any given
time so there will ever be only a very small number of pid files
in the directory.
TEST=pid_files_test
Change-Id: Id83a7f6138511f755ab47347c17b44d66a6a6964
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/487000
Reviewed-by: Martin Kustermann <kustermann@google.com>
Reviewed-by: Jaime Wren <jwren@google.com>
Slava Egorov
907c4838fd