None of these are legal in GLSL ES 1.0. Added a new test that previously
compiled without error. Started out with just assignment and equality,
then realized that sequence and ternary should be blocked, too.
Bug: skia:11323
Change-Id: I02691f819565afabeadbb12cab6c07acf40093f7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/370880
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
