[graphite] Add caching to ComputePathAtlas.

Adds a DrawAtlas managed by an internal atlas manager. If a shape
has a key we'll search and try to render to the DrawAtlas first, then
render to the ComputePathAtlas's texture as before.

Bug: b/305696981
Change-Id: I1513b4754a5e5e43cae8c7c0bd49bbec03e3a71a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/838739
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Arman Uguray <armansito@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
3 files changed