[skottie] Power-reduce paths (cubicTo -> lineTo)

For straight lines, Lottie exports control points conincident with the
vertices.  We can detect this case and emit more efficient lineTo's.

One wrinkle: we can only apply this power-reduction post-interpolation
(otherwise the path verbs and point count would not be guaranteed to
match).  Hence we store explicit shape data and defer the SkPath
conversion.

TBR=

Change-Id: I7818be464eabee6096d2078440843243a55c6e98
Reviewed-on: https://skia-review.googlesource.com/124800
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
5 files changed