This makes understanding and debugging the mapped names in the
translator interface easier.

TEST=shader_translator -u

Change-Id: I2457142a6f0a8baa623e80b00cc86c8df90e6718
Reviewed-on: https://chromium-review.googlesource.com/579968
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>