macOS V2 Sandbox: Allow launchservicesd in GPU process.

This resolves a hang in the GPU process by allowing launchservicesd
access in the V2 sandbox. The hang occurs because SkyLight performs
synchronous IPC to launchservicesd, which the sandbox blocks.

Bug: 812228
Change-Id: I871f05f081dc24f26c848492f91c1d4244bafc1d
Reviewed-on: https://chromium-review.googlesource.com/939858


Commit-Queue: Greg Kerr <kerrnel@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539606}