DevTools: Use short node selectors in the Event Listeners pane

R=eustas, pfeldman, vsevik
BUG=339085
NOTRY=true

Review URL: https://codereview.chromium.org/133233011

git-svn-id: svn://svn.chromium.org/blink/trunk@166257 bbb929c8-8fbe-4397-9dbb-9b2b20218538