Add counters for addEventListener/removeEventListener optional arguments

Per the FIXME in EventTarget.h, making these non-optional per spec has
failed once, so add counters to determine if it is now safe or not.

BUG=353484

Review URL: https://codereview.chromium.org/815503002

git-svn-id: svn://svn.chromium.org/blink/trunk@187434 bbb929c8-8fbe-4397-9dbb-9b2b20218538
3 files changed
tree: 3c95c68e940aa1405ad1d494e05129273b8d931d
  1. third_party/