== to ===, != to !==

These are preferred as they're more strict [0][1].

The exception is comparisons with null -- we sometimes want
== and != since they also match undefined.

[0] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Strict_equality

[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Strict_inequality

Change-Id: I7a391faab107f02c2486cdd59ebb415c7613526d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5420989


Reviewed-by: mmenke <mmenke@chromium.org>
Commit-Queue: Caleb Raitto <caraitto@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1282132}