This is a reland of 2a558f5675
Original change's description:
> [skottie] Add onTextProperty support into PropertyObserver.
>
> This effectively allows observing/modifying properties at the text document level. By default
> Bodymovin exports even static TextDocuments as a single keyframe, so the unit-tests have been
> updated to store the property handles for verification.
>
> Change-Id: Iab8bcb29cdc5626d1abc34593ee9967b543428eb
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/231681
> Commit-Queue: Florin Malita <fmalita@chromium.org>
> Reviewed-by: Florin Malita <fmalita@chromium.org>
Change-Id: I3231607e469dcc321fa5900500a21f0f101c299c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/232628
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Ben Wagner <bungeman@google.com>
3a543aafd4