SkPDF: SkPDFObject no longer reference-counted!

  * sed 's/sk_sp<SkPDF\(Object\|Array\|Dict\)>/std::unique_ptr<SkPDF\1>/g'
  * Added SkPDFMakeDict()
  * Let SkPDFMakeArray() take zero arguments.

Bug: skia:8630

Change-Id: I08dc11e974f1d71e09a33af6bdbcb5f01b07d186
Reviewed-on: https://skia-review.googlesource.com/c/179063
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Herb Derby <herb@google.com>
Auto-Submit: Hal Canary <halcanary@google.com>
23 files changed