Fix legacy SkSurface::MakeNull call

This prevents us from setting SK_DISABLE_LEGACY_SKSURFACE_FACTORIES

Change-Id: I75971bcfcc2290f2e6c34a67d16ecc7e86acf6af
Bug: skia:13983
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/698058
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
1 file changed