[skottie] Initial camera support

Camera layers introduce a top-level 3d camera/view matrix based on their
transform properties:

  * position - camera location
  * point of interest (stored as anchor point by BM) - camera direction
  * rotation - camera orientation

The perspective degree is controlled by a "zoom" camera property (which
corresponds to the view distance), and the composition dimensions.

Current limitations:

  * single camera track/layer
  * affects all layers (not just 3d-tagged layers)
  * parent layer transforms are likely not applied correctly

Bug: skia:
Change-Id: Ifc1b8b699ff09fa13b4804d18546b444d02e81c2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/201651
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
5 files changed