Issue 6504 - Remove useInlineStyles for now

lib/content/elemHideEmulation.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 586 matching lines @@
 {
   return patterns.some(pattern => pattern.dependsOnCharacterData);
 }
 
 function ElemHideEmulation(addSelectorsFunc, hideElemsFunc)
 {
   this.document = document;
   this.addSelectorsFunc = addSelectorsFunc;
   this.hideElemsFunc = hideElemsFunc;
   this.observer = new MutationObserver(this.observe.bind(this));
+
+  // This flag is supposed to indicate whether we should prefer setting the
+  // style attribute of the element over using CSS selectors. It is set by the
+  // web extension if the tabs.removeCSS API is available (Firefox 53+). But
+  // because of issues with performance (see #6422), we are ignoring the value
+  // of this flag for now; we always set the style attribute.
+  // https://issues.adblockplus.org/ticket/6504#comment:9
   this.useInlineStyles = true;
 }
 
 ElemHideEmulation.prototype = {
   isSameOrigin(stylesheet)
   {
     try
     {
       return new URL(stylesheet.href).origin == this.document.location.origin;
     }
@@ skipping 182 matching lines @@
         if (!this.useInlineStyles)
           evaluationTargets = null;
 
         generator = evaluate(pattern.selectors, 0, "",
                              this.document, cssStyles, evaluationTargets);
       }
       for (let selector of generator)
       {
         if (selector != null)
         {
-          if (!this.useInlineStyles)
+          for (let element of this.document.querySelectorAll(selector))
           {
-            selectors.push(selector);
-            selectorFilters.push(pattern.text);
-          }
-          else
-          {
-            for (let element of this.document.querySelectorAll(selector))
-            {
-              elements.push(element);
-              elementFilters.push(pattern.text);
-            }
+            elements.push(element);
+            elementFilters.push(pattern.text);
           }
         }
         if (performance.now() - cycleStart > MAX_SYNCHRONOUS_PROCESSING_TIME)
         {
           setTimeout(processPatterns, 0);
           return;
         }
       }
       pattern = null;
       return processPatterns();
@@ skipping 148 matching lines @@
           characterData: shouldObserveCharacterData(this.patterns),
           subtree: true
         }
       );
       this.document.addEventListener("load", this.onLoad.bind(this), true);
     }
   }
 };
 
 exports.ElemHideEmulation = ElemHideEmulation;