DevTools: Fix wrong pause reason when stepping into an event listener.

On StepInto we should not show "Paused on Event Listener".
The corresponding breakpoint may not even be active, so this status looks quite confusing.

BUG=432468
R=vsevik, yurys

Review URL: https://codereview.chromium.org/723543002

git-svn-id: svn://svn.chromium.org/blink/trunk@185362 bbb929c8-8fbe-4397-9dbb-9b2b20218538