Add methods to SkLayerDrawLooper to allow adding layers on top
as well as on the bottom.

This is more convenient for some callers who generate layers
from a data structure in bottom-to-top, rather than top-to-bottom,
order.

BUG=242529
R=tomhudson@chromium.org

Author: jbroman@chromium.org

Review URL: https://chromiumcodereview.appspot.com/15314003

git-svn-id: http://skia.googlecode.com/svn/trunk@9233 2bbb7eff-a529-9590-31e7-b0007b416f81
4 files changed