Open MessagePumpLibevent's pipe with O_CLOEXEC This prevents the pipe's fds from being leaked into child processes. This is a cherry-pick of https://crrev.com/80c77bfd86 . TEST=git cl try BUG=chromium:653930 Change-Id: I1d9ea26e41a23dc7ca5cd6d4b2133a2e69b1259c Reviewed-on: https://chromium-review.googlesource.com/395446 Commit-Ready: Luis Hector Chavez <[email protected]> Tested-by: Luis Hector Chavez <[email protected]> Reviewed-by: Luis Hector Chavez <[email protected]>