GLES2: Reformat entry point header. This should simplify the diff with the auto-gen patch. BUG=angleproject:1309 Change-Id: Ibea503f236e7dc07d0862e20f77e866d6ec1f316 Reviewed-on: https://chromium-review.googlesource.com/489081 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org>