Unregister all scriptlets when disabling uBO on a specific site

Related issue:
uBlockOrigin/uBlock-issues#3083

This will not completely eliminate the issue but it should
lower the likelihood it will occur -- so at least uBO can
still benefit from reliable scriptlet execution in Firefox.

src/js/scriptlet-filtering.js

@@ -45,10 +45,13 @@ const contentScriptRegisterer = new (class {
  constructor() {
  this.hostnameToDetails = new Map();
  if ( browser.contentScripts === undefined ) { return; }
- onBroadcast(msg => {
+ this.bc = onBroadcast(msg => {
  if ( msg.what !== 'filteringBehaviorChanged' ) { return; }
- if ( msg.direction > 0 ) { return; }
- if ( msg.hostname ) { return this.flush(msg.hostname); }
+ const direction = msg.direction || 0;
+ if ( direction > 0 ) { return; }
+ if ( direction >= 0 && msg.hostname ) {
+ return this.flush(msg.hostname);
+ }
  this.reset();
  });
  }
@@ -78,13 +81,15 @@ const contentScriptRegisterer = new (class {
  return false;
  }
  unregister(hostname) {
+ if ( hostname === '' ) { return; }
  if ( this.hostnameToDetails.size === 0 ) { return; }
  const details = this.hostnameToDetails.get(hostname);
  if ( details === undefined ) { return; }
  this.hostnameToDetails.delete(hostname);
  this.unregisterHandle(details.handle);
  }
  flush(hostname) {
+ if ( hostname === '' ) { return; }
  if ( hostname === '*' ) { return this.reset(); }
  for ( const hn of this.hostnameToDetails.keys() ) {
  if ( hn.endsWith(hostname) === false ) { continue; }

src/js/ublock.js

@@ -148,7 +148,7 @@ const matchBucket = function(url, hostname, bucket, start) {
  }
  bucket.push(directive);
  this.saveWhitelist();
- filteringBehaviorChanged({ hostname: targetHostname });
+ filteringBehaviorChanged({ hostname: targetHostname, direction: -1 });
  return true;
  }