Translator: Initialize out arguments too for WebGL Local variables were initialized for WebGL, but not `out` arguments. However, `out` arguments completely overwrite the passed-in variable at call site, so they should also be zeroed out. Bug: chromium:1425685 Change-Id: Ib2f61a962eea74c4933aafa4d5ad377189cec578 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4375137 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>