Scrub SkPictureData/SkPictureRecord

- replace manual ref fiddling with smart types
- remove unused SkPictureData::fBitmapImageRefs
- remove the preallocation in new_array_from_buffer (to prevent
  fuzzer OOMs)

Bug: skia:7937
Change-Id: I50f49fa8e594a138ea09c22f7bf73cf57ec006ff
Reviewed-on: https://skia-review.googlesource.com/128309
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
4 files changed