Revert "hide picture virtuals (no public callers)"

This reverts commit 8005bff7e631a269f0dfaae93ff9963dc0e5ff39.

Reason for revert: hwui, flutter, and headless blink in G3 all still using these.

Original change's description:
> hide picture virtuals (no public callers)
> 
> This prepares the way for a clean impl of a "placeholder" picture that never unrolls
> 
> Bug: skia:
> Change-Id: I3b5785c5c94432b54e9a7dc280b2a6e716592473
> Reviewed-on: https://skia-review.googlesource.com/100260
> Commit-Queue: Mike Reed <reed@google.com>
> Reviewed-by: Mike Klein <mtklein@chromium.org>

TBR=mtklein@chromium.org,mtklein@google.com,reed@google.com

Change-Id: I385789dd420588ea9a9390c8a44c6ecb96c7f358
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/100880
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
15 files changed