I16x8SConvertI32x4, I16x8UConvertI32x4,
I8x16SConvertI16x8, I8x16UConvertI16x8

Change-Id: Iab462c3fb6c60de7b54a925e438862362605fe8d
Reviewed-on: https://chromium-review.googlesource.com/1016178Reviewed-by: Aseem Garg <aseemgarg@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Jing Bao <jing.bao@intel.com>
Cr-Commit-Position: refs/heads/master@{#52771}