Add ability to trigger cookie removal on specific events

As discussed with filter list volunteers.

Related discussion:
uBlockOrigin/uBlock-discussions#834

assets/resources/scriptlets.js

@@ -2703,17 +2703,25 @@ function cookieRemover(
  if ( typeof needle !== 'string' ) { return; }
  const safe = safeSelf();
  const reName = safe.patternToRegex(needle);
- const removeCookie = function() {
+ const extraArgs = safe.getExtraArgs(Array.from(arguments), 1);
+ const throttle = (fn, ms = 1000) => {
+ if ( throttle.timer !== undefined ) { return; }
+ throttle.timer = setTimeout(( ) => {
+ throttle.timer = undefined;
+ fn();
+ }, ms);
+ };
+ const removeCookie = ( ) => {
  document.cookie.split(';').forEach(cookieStr => {
- let pos = cookieStr.indexOf('=');
+ const pos = cookieStr.indexOf('=');
  if ( pos === -1 ) { return; }
- let cookieName = cookieStr.slice(0, pos).trim();
- if ( !reName.test(cookieName) ) { return; }
- let part1 = cookieName + '=';
- let part2a = '; domain=' + document.location.hostname;
- let part2b = '; domain=.' + document.location.hostname;
+ const cookieName = cookieStr.slice(0, pos).trim();
+ if ( reName.test(cookieName) === false ) { return; }
+ const part1 = cookieName + '=';
+ const part2a = '; domain=' + document.location.hostname;
+ const part2b = '; domain=.' + document.location.hostname;
  let part2c, part2d;
- let domain = document.domain;
+ const domain = document.domain;
  if ( domain ) {
  if ( domain !== document.location.hostname ) {
  part2c = '; domain=.' + domain;
@@ -2722,8 +2730,8 @@ function cookieRemover(
  part2d = '; domain=' + domain.replace('www', '');
  }
  }
- let part3 = '; path=/';
- let part4 = '; Max-Age=-1000; expires=Thu, 01 Jan 1970 00:00:00 GMT';
+ const part3 = '; path=/';
+ const part4 = '; Max-Age=-1000; expires=Thu, 01 Jan 1970 00:00:00 GMT';
  document.cookie = part1 + part4;
  document.cookie = part1 + part2a + part4;
  document.cookie = part1 + part2b + part4;
@@ -2738,6 +2746,11 @@ function cookieRemover(
  }
  });
  };
+ if ( extraArgs.when === 'scroll' ) {
+ document.addEventListener('scroll', ( ) => {
+ throttle(removeCookie);
+ }, { passive: true });
+ }
  removeCookie();
  window.addEventListener('beforeunload', removeCookie);
 }