Make skerr.Wrap work pass-through nil errors
Make skerr.Wrap work pass-through nil errors

Change-Id: Iff2d1bf6f3bca0565beb149360586ed962401a54
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/236299
Commit-Queue: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Auto-Submit: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot