Attempt skipping D3D11 shader optimization if compilation fails. BUG=angle:648,chromium:371868 Change-Id: I1de854aad6e002bd1349f08eb8d6b597c535c90b Reviewed-on: https://chromium-review.googlesource.com/199312 Tested-by: Nicolas Capens <nicolascapens@chromium.org> Reviewed-by: Brandon Jones <bajones@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>