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/+/2892286Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Alexis Hétu <sugoi@chromium.org>