Remove the pause argument from setActive

Nothing reads the value even though we pass it all the way down. This
also exposes that all the code related to SimulatedClickMouseEventOptions
was dead.

Review URL: https://codereview.chromium.org/69673003

git-svn-id: svn://svn.chromium.org/blink/trunk@161772 bbb929c8-8fbe-4397-9dbb-9b2b20218538