Perform the same analytic blur calculation on the GPU that we do on the CPU.  Results in significant performance gains when using Ganesh to render drop shadows in Chrome.

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

Author: humper@google.com

Review URL: https://codereview.chromium.org/119343003

git-svn-id: http://skia.googlecode.com/svn/trunk@13210 2bbb7eff-a529-9590-31e7-b0007b416f81
7 files changed