TypeScriptify EventListenersUtils.js
TypeScriptify EventListenersUtils.js

R=szuend@chromium.org

Bug: 1011811
Change-Id: I240884ffc6a362f1ec1c2d4854ed355f64d9b778
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2550687
Reviewed-by: Tim van der Lippe <dba8716ee7f8d16236046f74d2167cb94410f6ed@chromium.org>
Commit-Queue: Paul Lewis <8915f5d5c39a08c5a3e8a8d7314756e4580816f9@chromium.org>

ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend