Add --runOnce flag to run benchs once in release or to force convergence in debug

R=mtklein@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/242103013

git-svn-id: http://skia.googlecode.com/svn/trunk@14292 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed