Forcing the release ensures we always manually deallocate resources,
and allows us to compile for different shader model versions after
releasing the renderer.

BUG=angle:619

Change-Id: I0c9d68a454c7779a024f4fcc4f4987c2abe12e60
Reviewed-on: https://chromium-review.googlesource.com/196820Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Nicolas Capens <nicolascapens@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>