Metal: Fix validation for anonymous struct arrays Fix validation failure for accessing an element of array of anonymous struct. SeparateCompoundStructDeclarations would create new Structures to name unnamed structures. The Structure instance of the array index accessor node was incorrect, it was the old Structure. Use same pattern as in SeparateStructFromUniformDeclarations. Bug: angleproject:8551 Change-Id: I04684e5ad99cc2b9038a0cc21c7eefcc6cf247df Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5310074 Commit-Queue: Kimmo Kinnunen <kkinnunen@apple.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org> Auto-Submit: Kimmo Kinnunen <kkinnunen@apple.com>