Vulkan: Use DontCare if attachment is invalidated If an attachment is invalidated, there is no need to preserve the old content. NONE means old content is still preserved, DontCare means discard old content. In this case we do want to discard instead of preserve old content. Bug: b/243711628 Change-Id: I242ac86db6993574b5627d61f7185d155beec0ba Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3888938 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Auto-Submit: Charlie Lao <cclao@google.com> Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Yuxin Hu <yuxinhu@google.com>