chromeos: fix possible deadlock during shutdown

This makes ~AshService shutdown parts of GpuHost early in shutdown in hopes of
avoiding a deadlock between the raster thread and main thread.

BUG=none
TEST=none

Change-Id: I438ce9ec9eebf025abf7a5dc0f546792d2c6c9e7
Reviewed-on: https://chromium-review.googlesource.com/1140735
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575759}
4 files changed