Move max-shader-compile-threads state out of LocalState While this state is indeed context-local, setting it calls into the backend (GL backend specifically, where it forwards the call to the driver). The call to set this state is rare and now worth the risk associated with making it lockless. Bug: angleproject:8224 Change-Id: I3af395721fa18b9345698870c0da63e8cac83610 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4666355 Reviewed-by: Igor Nazarov <i.nazarov@samsung.com> Auto-Submit: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Charlie Lao <cclao@google.com>