DevTools: Capture async stacks for event listeners.

BUG=272416
R=yurys@chromium.org

Review URL: https://codereview.chromium.org/114033002

git-svn-id: svn://svn.chromium.org/blink/trunk@164080 bbb929c8-8fbe-4397-9dbb-9b2b20218538