Plumb layer size information and add machinery for retrieving layer
content as an SkPicture.
Implement the effect in SkSL.
Current limitations:
* displacement source layer must be above (on top in stacking order)
of the target layer
* if animated, the displacement layer timeline (in/out points) must
fully cover the target layer timeline
* Hue/Sat/Lightness selectors are not supported at the moment
These will be addressed in follow-up CLs.
Note: Bodymovin does not export hidden layers by default; if the
displacement source layer is hidden, one should select the "Hidden"
export option.
Change-Id: I11a5c760a9df1e75835a51371f60d5b798e7e38a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/314798
Commit-Queue: Florin Malita <fmalita@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
