Make blurcircles2 run as a benchmark.

In bench mode it does not draw the comparison paths (or line separators). It also randomly perturbs the blur and circle radii to avoid trivially hitting the same cache entries and each repetition.

BUG=skia:5224
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1985713002

Review-Url: https://codereview.chromium.org/1985713002
1 file changed