Make validation make straight calls to ErrorSet ... and avoid going through the context (just to get a const cast). This change is also in preparation for an follow up where some entry points directly use ErrorSet and don't access context at all. Bug: angleproject:8224 Change-Id: Idef0a88d9407870e7a84b4fe6967fbff175c269b Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4678350 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>