This was broken due to a simple omission in deep copying swizzle AST
nodes.

It was found that several if not most OpenGL drivers also have some
issue related to this, so the end2end test is suppressed on many
OpenGL platforms. Intel Windows driver seems to be behaving correctly.

BUG=angleproject:1921
TEST=angle_end2end_tests

Change-Id: Ieefcedc2f2e36c3d8b607c28e449b696b8ad6892
Reviewed-on: https://chromium-review.googlesource.com/449717Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>