Guard ID3DUserDefinedAnnotation access in DebugAnnotator11. ID3DUserDefinedAnnotation is not thread-safe, like ID3D11DeviceContext, however, it's being accessed from WorkerThread for parallel compilation, thus guard it with mutex lock. Bug: angleproject:3493 Change-Id: Ic7cc7fe03675174e054fe1e11d8d9e05abc716a5 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1709726 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Yuly Novikov <ynovikov@chromium.org>