Add benchmark for PremultiplyAlpha and UnpremultiplyAlpha in Skia

BUG=248549
R=tomhudson@chromium.org, bsalomon@chromium.org, reed@google.com, noel@chromium.org, tomhudson@google.com

Author: jun.a.jiang@intel.com

Review URL: https://chromiumcodereview.appspot.com/16654004

git-svn-id: http://skia.googlecode.com/svn/trunk@9569 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed