Add array bounds checks for WebGL shaders WebGL shaders may contain OOB array accesses which in turn cause undefined behavior, which may result in security issues. This was detected as an UNKNOWN READ by UBSAN while testing with SwANGLE. Bug: chromium:1189110 Change-Id: I00f56e771ed0c675abb465fc3a3dc9d62ea8ed51 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2892286 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Alexis Hétu <sugoi@chromium.org>