Remove SkCrossContextImageData and all support code

Bug: skia:
Change-Id: I8eb8cef5456c05a8e314d8404698893c7af82d13
Reviewed-on: https://skia-review.googlesource.com/16368
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
25 files changed