This moves GLSL output specific code from the Compiler class to the
GLSL/ESSL translators.

BUG=angleproject:865

Change-Id: I2d552e9cdb41f7d8ddfee7b0249a99d629a6d7d7
Reviewed-on: https://chromium-review.googlesource.com/255471Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Olli Etuaho <oetuaho@nvidia.com>