Make ANGLE_texture_usage enableable. BUG=angleproject:1523 Change-Id: I4e6e4ec6ae7cfb616869373b62dc455d0c5c8c09 Reviewed-on: https://chromium-review.googlesource.com/744444 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org>