Add gms and benchmarks for drawing blurry round rects.

Further changes (https://codereview.chromium.org/48623006) will change
the speed at which the bench draws and the drawing of the gm (the gm
change is small).

One of these round rects causes slow drawing in a webpage that we have
observed.

BUG=https://b.corp.google.com/issue?id=11174385

Review URL: https://codereview.chromium.org/52793005

git-svn-id: http://skia.googlecode.com/svn/trunk@12133 2bbb7eff-a529-9590-31e7-b0007b416f81
4 files changed