Add loopSKP flag to nanobench

Add loopSKP flag to nanobench

Adds a loopSKP flag that forces SKPBenches to draw with only 1 loop.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/b4022965a280dd1ed64d6103dd29e2189abe6e00

[Chris Dalton, 2015-06-24 18:47:43]

cdalton@nvidia.com changed reviewers:
+ bsalomon@google.com, joshualitt@google.com, mtklein@google.com

[Chris Dalton, 2015-06-24 18:47:44]

Hey guys, just curious if you'd be OK with something like this.

It also ended up being easiest to modify SKPAnimationBench so every step of the
animation is a "loop", so now it prints the average time to draw one frame
instead of the cumulative time to draw all frames.

[bsalomon, 2015-06-25 15:50:46]

lgtm

[Chris Dalton, 2015-06-25 17:45:52]

The CQ bit was checked by cdalton@nvidia.com

[Chris Dalton, 2015-06-25 17:45:52]

The patchset sent to the CQ was uploaded after l-g-t-m from bsalomon@google.com
Link to the patchset: https://codereview.chromium.org/1203193002/#ps60001
(title: "rebase")

[commit-bot: I haz the power, 2015-06-25 17:46:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1203193002/60001

[commit-bot: I haz the power, 2015-06-25 17:46:08]

The author cdalton@nvidia.com has not signed Google Contributor License
Agreement. Please visit https://cla.developers.google.com to sign and manage
CLA.

[commit-bot: I haz the power, 2015-06-25 17:52:03]

Committed patchset #4 (id:60001) as
https://skia.googlesource.com/skia/+/b4022965a280dd1ed64d6103dd29e2189abe6e00