Culling API

*** SKP format breaking change ***

Adding a couple of culling primitives: pushCull(SkRect) & popCull().

These are currently only plumbed for SKP playback quickreject.

At record time, we perform a couple of optimizations to trim down the
number of redundant culls:

  * collapse empty pushCull/popCull pairs
  * skip pushCull/popCull pairs nested within an identical cull rect

Things still missing/to consider:

  * use an inlineable, simplified quickreject (Mike's old prototype)
  * debugger visualization for cull boxes
  * BBH integration: the initial prototype had some minimal BBH support,
    but since the optimizations required expensive rewinds and culling
    is expected to be a BBH alternative, it got dropped.

R=bsalomon@google.com, reed@google.com, robertphillips@google.com, caryclark@google.com, tomhudson@google.com, iancottrell@google.com

Author: fmalita@chromium.org

Review URL: https://codereview.chromium.org/138013009

git-svn-id: http://skia.googlecode.com/svn/trunk@13611 2bbb7eff-a529-9590-31e7-b0007b416f81
14 files changed