Issue 6504 - Remove element hiding emulation code related to style sheets

lib/content/elemHideEmulation.js

Index: lib/content/elemHideEmulation.js
===================================================================
--- a/lib/content/elemHideEmulation.js
+++ b/lib/content/elemHideEmulation.js
@@ -602,22 +602,28 @@
 {
   return patterns.some(pattern => pattern.dependsOnCharacterData);
 }
 
 class ElemHideEmulation
 {
   constructor(addSelectorsFunc, hideElemsFunc)
   {
+    // Note: The first parameter to this constructor was previously used for
+    // injecting style sheets into the document for :-abp-properties() but this
+    // code has since moved on to use inline styles for all types of emulation
+    // filters (#6610). Nevertheless, there is a plan to go back to using style
+    // sheets on platforms that support the tabs.removeCSS API (#6504); hence
+    // this first parameter remains for now.
+
     this._filteringInProgress = false;
     this._lastInvocation = -MIN_INVOCATION_INTERVAL;
     this._scheduledProcessing = null;
 
     this.document = document;
-    this.addSelectorsFunc = addSelectorsFunc;
     this.hideElemsFunc = hideElemsFunc;
     this.observer = new MutationObserver(this.observe.bind(this));
   }
 
   isSameOrigin(stylesheet)
   {
     try
     {
@@ -710,19 +716,16 @@
    */
   _addSelectors(stylesheets, mutations, done)
   {
     if (testInfo)
       testInfo.lastProcessedElements.clear();
 
     let patterns = filterPatterns(this.patterns, {stylesheets, mutations});
 
-    let selectors = [];
-    let selectorFilters = [];
-
     let elements = [];
     let elementFilters = [];
 
     let cssStyles = [];
 
     // If neither any style sheets nor any DOM mutations have been specified,
     // do full processing.
     if (!stylesheets && !mutations)
@@ -778,18 +781,16 @@
     let processPatterns = () =>
     {
       let cycleStart = performance.now();
 
       if (!pattern)
       {
         if (!patterns.length)
         {
-          if (selectors.length > 0)
-            this.addSelectorsFunc(selectors, selectorFilters);
           if (elements.length > 0)
             this.hideElemsFunc(elements, elementFilters);
           if (typeof done == "function")
             done();
           return;
         }
 
         pattern = patterns.shift();