Issue 6618 - Prefer CSS selectors for plain emulation filters

lib/content/elemHideEmulation.js

Index: lib/content/elemHideEmulation.js
===================================================================
--- a/lib/content/elemHideEmulation.js
+++ b/lib/content/elemHideEmulation.js
@@ -222,16 +222,18 @@
 
 function PlainSelector(selector)
 {
   this._selector = selector;
   this.maybeDependsOnAttributes = /[#.]|\[.+\]/.test(selector);
 }
 
 PlainSelector.prototype = {
+  preferHideWithSelector: true,
+
   /**
    * Generator function returning a pair of selector
    * string and subtree.
    * @param {string} prefix the prefix for the selector.
    * @param {Node} subtree the subtree we work on.
    * @param {StringifiedStyle[]} styles the stringified style objects.
    */
   *getSelectors(prefix, subtree, styles)
@@ -403,17 +405,17 @@
   this.text = text;
 }
 
 Pattern.prototype = {
   isSelectorHidingOnlyPattern()
   {
     return getCachedPropertyValue(
       this, "_selectorHidingOnlyPattern",
-      () => this.selectors.some(selector => selector.preferHideWithSelector) &&
+      () => this.selectors.every(selector => selector.preferHideWithSelector) &&
             !this.selectors.some(selector => selector.requiresHiding)
     );
   },
 
   get dependsOnStyles()
   {
     return getCachedPropertyValue(
       this, "_dependsOnStyles",