SkRecord: make culling work if SkRecordAnnotateCullingPairs is called.

SkRecord: make culling work if SkRecordAnnotateCullingPairs is called.

  - Allow stateful functors; allow visit()/mutate() at a given index; add count().
  - Annotate cull push/pop pairs on the PushCull records.  (tested)
  - Use those annotations to skip ahead in SkRecordDraw.   (not yet tested beyond dm --skr)
  - Make SkRecordDraw a function, move its implementation to a .cpp.

BUG=skia:2378
R=fmalita@chromium.org, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/229523002

git-svn-id: http://skia.googlecode.com/svn/trunk@14101 2bbb7eff-a529-9590-31e7-b0007b416f81