Add nanosecond timer.

I've been finding it hard to get enough resolution out of our existing timers when measuring really tiny pictures.

BUG=skia:2378
R=bsalomon@google.com, mtklein@google.com, bungeman@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/250243002

git-svn-id: http://skia.googlecode.com/svn/trunk@14362 2bbb7eff-a529-9590-31e7-b0007b416f81
6 files changed