- add validate()
- make add() and remove() strict
- fill in maybeShrink()
- make grow and shrink thresholds configurable.
- fix issue where we were getting filled with deleted items - we need to count them as occupied when determining if we should grow
BUG=
R=reed@google.com
Review URL: https://codereview.chromium.org/22571010
git-svn-id: http://skia.googlecode.com/svn/trunk@10677 2bbb7eff-a529-9590-31e7-b0007b416f81
