Make addEventListener/removeEventListener arguments non-optional

Intent to Implement and Ship:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/3rsQQJvhY8k/P2cAFq3hAwAJ

BUG=353484

Review URL: https://codereview.chromium.org/1461993002

Cr-Commit-Position: refs/heads/master@{#361316}
13 files changed