Regression test for class removal.

Added test to avoid future regressions in class removal.

R=ojan
BUG=344376

Review URL: https://codereview.chromium.org/165723006

git-svn-id: svn://svn.chromium.org/blink/trunk@167364 bbb929c8-8fbe-4397-9dbb-9b2b20218538