Previously, we skipped adding to the names map if it was a prefixed
name. This prevents the mapping of glsl es to glsl names from being
accessible by an outside client.

Bug: b/158533223
Change-Id: Ib1d1e229ceb6d836df8dd0c30ea848b081a40cad
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2240637Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Lingfeng Yang <lfy@google.com>
Commit-Queue: Lingfeng Yang <lfy@google.com>