MetalSurfaceEXT and MacOSSurfaceMVK were inheriting incorrectly from the base class MetalSurface, and were improperly initialized. Additionally, none of the drawables were ever released, meaning there were no re-used drawables. Add an @autoreleasepool around the drawable retrival path, as per the spec: https://developer.apple.com/documentation/quartzcore/cametallayer?language=objc#3172024 Bug: chromium:1015454 Change-Id: Idd2f1842977a6f5dccecf31d152d454a44e9261c Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/37948Reviewed-by: Alexis Hétu <sugoi@google.com> Tested-by: Jonah Ryan-Davis <jonahr@google.com>
