Add MakeCrossContextFromPixmap

This operates just like MakeCrossContextFromEncoded, but starting from
raster data. This version is defensive (always uses copies if a raster
image needs to be made).

Bug: skia:
Change-Id: Ibc2b9a235c89a41fbbfd022d943f15ac212d0677
Reviewed-on: https://skia-review.googlesource.com/68205
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
4 files changed