change benchmark to use surfaces instead of devices to specify its backends

BUG=skia:
R=mtklein@google.com

Review URL: https://codereview.chromium.org/153133002

git-svn-id: http://skia.googlecode.com/svn/trunk@13297 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed