This is a first step towards auto-generating more entry point files.

BUG=angleproject:1309

Change-Id: Ic75a627feb91c19b6bb398a6f9f1a37b603dea14
Reviewed-on: https://chromium-review.googlesource.com/483425
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>