calculate cull rects for SkMiniPictures

This is the other half of https://skia-review.googlesource.com/c/7874/,
adding the cull-shrinking feature of SkBigPictures to SkMiniPictures.

Like SkBigPictures, shrink only when we're asked to build an R-tree.
(We don't actually build a tree for one rect, of course.)

We could do unconditionally, but SkPictureImageFilter uses the cull rect
as its crop.  It's unclear to me what this image filter unit test I've
changed here was intending... had it had two draws we would have shrunk
its cull, but because it was hitting the 1-draw SkMiniPicture path it
kept the larger user-supplied cull.

As the test doesn't appear to have been written with cull shrinking in
mind, I've removed its SkRTreeFactory to keep that feature explicitly
disabled there.

BUG=skia:5974

Change-Id: I4118d2e85f2a69adef2e7a7fa9b9b8c17607a94f
Reviewed-on: https://skia-review.googlesource.com/12624
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>

0 files changed, 0 insertions, 0 deletions