Perform multi core rendering in bench_pictures.

Add a flag in SkGPipeWriter for threadsafe drawing.

Add a deferred pipe controller to SamplePipeControllers, which can
be called to play back in multiple threads.

Depends on http://codereview.appspot.com/6459105/

Review URL: https://codereview.appspot.com/6482068

git-svn-id: http://skia.googlecode.com/svn/trunk@5371 2bbb7eff-a529-9590-31e7-b0007b416f81
13 files changed