Test for ARM bug with dynamic stencil write mask Bug: b/240755039 Change-Id: If7025f3b2450735a099da3cc11524f778f2ac654 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3812559 Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>