Make sure the new enums are invalid before the extension is enabled.
Add a angle_end2end_test for that.

Bug: angleproject:4394, chromium:1058744
Change-Id: Ib88f6159294dab2eb7d3662b96c44424ab132782
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2205179Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Shrek Shao <shrekshao@google.com>