add diff viewer website

- adjust PMetric output to be percentage

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

Review URL: https://codereview.chromium.org/18132007

git-svn-id: http://skia.googlecode.com/svn/trunk@9942 2bbb7eff-a529-9590-31e7-b0007b416f81
4 files changed