Delete unnecessary SkSurface_Base API

BUG=skia:

Change-Id: I1263d390ffc1660a561b03c9dd866390754e59af
Reviewed-on: https://skia-review.googlesource.com/5231
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>
3 files changed