Issue 5773 - Older Opera and Chrome don't have an iterable CSSRuleList

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 412 matching lines @@
       let stylesheet = stylesheets[i];
       // Explicitly ignore third-party stylesheets to ensure consistent behavior
       // between Firefox and Chrome.
       if (!this.isSameOrigin(stylesheet))
         continue;
 
       let rules = stylesheet.cssRules;
       if (!rules)
         continue;
 
-      for (let rule of rules)
+      // Chrome < 51 doesn't have an iterable CSSRuleList
+      // https://issues.adblockplus.org/ticket/5773
+      for (let i = 0; i < rules.length; i++)
       {
+        let rule = rules[i];
         if (rule.type != rule.STYLE_RULE)
           continue;
 
         cssStyles.push(stringifyStyle(rule));
       }
     }
 
     let {document} = this.window;
 
     let patterns = this.patterns.slice();
@@ skipping 162 matching lines @@
             subtree: true
           }
         );
         document.addEventListener("load", this.onLoad.bind(this), true);
       }
     });
   }
 };
 
 exports.ElemHideEmulation = ElemHideEmulation;