SkPDF: use more vector<>, more sk_sp<>, cleanup.

All PDFs are identical.

Change-Id: If2af8519a6440a5b61f91bf78fc7ae241f728183
Reviewed-on: https://skia-review.googlesource.com/151220
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
Auto-Submit: Hal Canary <halcanary@google.com>
20 files changed