Restore a default timer to bench_pictures.

https://codereview.chromium.org/19862002 removed the default timer
to display from PictureBenchmark. Restore a default by putting it
in the flag description.

R=mtklein@google.com

Review URL: https://codereview.chromium.org/21567005

git-svn-id: http://skia.googlecode.com/svn/trunk@10516 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed