Remove global SkRandoms from ChartBench.

TSAN picked them up while running DM.

BUG=skia:1792
R=bsalomon@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/278523005

git-svn-id: http://skia.googlecode.com/svn/trunk@14641 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed