Add no-op NULL picture to bench_record.

Add no-op NULL picture to bench_record.

Defaults of out/Release/bench_record are still fine; NULL's not too far off
from stable at 900 loops.  But for focus on NULL, I'd recommend
something like out/Release/bench_record --loops 100000 --skps.

Also: fail on failures, print 2 significant digits instead of fixed 4.2.

BUG=skia:1850
R=tomhudson@chromium.org

Author: mtklein@google.com

Review URL: https://codereview.chromium.org/136873002

git-svn-id: http://skia.googlecode.com/svn/trunk@13054 2bbb7eff-a529-9590-31e7-b0007b416f81