Simplify benchmark internal API.

Simplify benchmark internal API.

I'm not quite sure why I wrote such a convoluted API with setLoops()/getLoops().
This replaces it with a loops argument passed to onDraw().

This CL is largely mechanical translation from the old API to the new one.
MathBench used this->getLoops() outside onDraw(), which seems incorrect.  I
fixed it.

BUG=
R=djsollen@google.com

Author: mtklein@google.com

Review URL: https://codereview.chromium.org/99893003

git-svn-id: http://skia.googlecode.com/svn/trunk@12466 2bbb7eff-a529-9590-31e7-b0007b416f81