Switched Context::errors() over to a field access

Now that Context owns the errors pointer, there is no magic behind its
accessor and no reason not to just use a straight field access.

Change-Id: I3f771f458ffdaf95d6289ba5767535a78126cc0b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/441312
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
34 files changed