Add compiler support for shared memory The patch adds handling of the 'shared' qualifier in the shader compiler. BUG=angleproject:1442 TEST=angle_unittests Change-Id: Iaa288026af0faf2a30e40495faa6ea1f5ff02323 Reviewed-on: https://chromium-review.googlesource.com/413200 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>