[BGPT] Add a fast-path for transform-origin changes.

This patch adds a fast-path for updating composited transform-origin
changes without requiring a PaintArtifactCompositor update. This
closely follows the approach of https://crrev.com/651338.

Bug: 952473
Change-Id: I8b82909c1761a7aa16705813207739d29596b0d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1580260
Commit-Queue: Philip Rogers <pdr@chromium.org>
Auto-Submit: Philip Rogers <pdr@chromium.org>
Reviewed-by: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653749}