Flattening branch-heavy shaders that contained no loops caused regressions. As a temporary workaround we only flatten ifs when there exists a loop. BUG=395048 Change-Id: I95c40f0249643b98c62304a0f2a4563561d1fbbc Reviewed-on: https://chromium-review.googlesource.com/228722Reviewed-by: Shannon Woods <shannonwoods@chromium.org> Tested-by: Corentin Wallez <cwallez@chromium.org>
