Adds console.* APIs for workers.

BUG=63383

Review URL: https://chromiumcodereview.appspot.com/23145003

git-svn-id: svn://svn.chromium.org/blink/trunk@156665 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Expose isClickable attribute, and make clickable anchors have a link role.

This matches what Firefox does.

BUG=120946

Review URL: https://chromiumcodereview.appspot.com/23153004

git-svn-id: svn://svn.chromium.org/blink/trunk@156666 bbb929c8-8fbe-4397-9dbb-9b2b20218538