Correct LottieWeb drawing params

The tiles are now centered in a 200 x 200 box.
Additionally, the frames drawn should now
match how the seeking happens (before, we would
try to draw frame *index* 300 when there were only
300 frames)

I renamed a variable in DmSrcSink because it initially
confused me as the purpose of it.

Bug: skia:
Change-Id: I8552a24727326cd8714dfd1c7794a0c4b0a418cb
Reviewed-on: https://skia-review.googlesource.com/150126
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
2 files changed