Initial picture shader implementation

This CL adds an SkPictureShader class to support SkPicture-based
patterns.

The implementation renders the picture into an SkBitmap tile and then
delegates to SkBitmapProcShader for the actual operation.

R=bsalomon@google.com, reed@google.com, robertphillips@google.com

Author: fmalita@chromium.org

Review URL: https://codereview.chromium.org/221923007

git-svn-id: http://skia.googlecode.com/svn/trunk@14085 2bbb7eff-a529-9590-31e7-b0007b416f81
7 files changed