This map lives in formatutils.cpp, and maps from a {format,type} to
an internal format. Convert this into generated code.

BUG=angleproject:1389

Change-Id: Ib12750d83d3f8cf8794d6668874cb025f856b5d4
Reviewed-on: https://chromium-review.googlesource.com/392207
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>