move SkWriter32.h to src

Bug: skia:
Change-Id: If110f1716d2ad3b967aadca1c61d3e22386e17b1
Reviewed-on: https://skia-review.googlesource.com/94862
Commit-Queue: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
2 files changed