Using just --disable-es3-apis will correctly disable WebGL2 support but still create native ES3 contexts.

Using just --disable-es3-gl-context will create ES2 contexts but result in assertion failures when creating WebGL2 contexts because the check to disable WebGL2/ES3 context creation only checks for the --disable-es3-apis flag (ContextGroup::Initialize).

I'm not sure what the correct solution is, maybe one of these flags should be removed.

Assigning to Mo because he's done the most work with these flags.