Simplify burst handling. Scripts should just add to burst (if
they want to handle programmatic bursting, as well).
Update most effects to handle dynamic updates to position better,
and add a sample effect meant to be used with mouse tracking.
Change-Id: Ia302e1d04e62e2b07974807c44067786cc10a8ad
Bug: skia:9513
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/248798
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>