Make GrContext cache the gpu paths

Creating paths for nv_path_rendering is costly. Try to reduce this
cost by caching paths based on the SkPath "hash" (i.e. SkPathRef
generation id) and stroke properties.

Adds the paths to GrContext::fTextureCache instance. Later this should
be renamed and the GrContext API should reflect the nature of the cache
better.

R=bsalomon@google.com, mtklein@google.com

Author: kkinnunen@nvidia.com

Review URL: https://codereview.chromium.org/26557003

git-svn-id: http://skia.googlecode.com/svn/trunk@12083 2bbb7eff-a529-9590-31e7-b0007b416f81
8 files changed