Add perf tests for getAttribute("role") and setAttribute("role").

We have already perf tests for getAttribute("id") and getAttribute("id"). Rare
attributes have different code path unlike important attributes such as
id/name/class/style. So this CL adds new perf tests for rare attributes.

BUG=350380

Review URL: https://codereview.chromium.org/196723018

git-svn-id: svn://svn.chromium.org/blink/trunk@169248 bbb929c8-8fbe-4397-9dbb-9b2b20218538