Issue 6505 - Make selector parameter in makeSelector optional

lib/content/elemHideEmulation.js

Index: lib/content/elemHideEmulation.js
===================================================================
--- a/lib/content/elemHideEmulation.js
+++ b/lib/content/elemHideEmulation.js
@@ -31,17 +31,17 @@
 {
   let {children} = node.parentNode;
   for (let i = 0; i < children.length; i++)
     if (children[i] == node)
       return i + 1;
   return 0;
 }
 
-function makeSelector(node, selector)
+function makeSelector(node, selector = "")
 {
   if (node == null)
     return null;
   if (!node.parentElement)
   {
     let newSelector = ":root";
     if (selector)
       newSelector += " > " + selector;
@@ -262,17 +262,17 @@
     return this._innerSelectors.some(
       selector => selector.maybeDependsOnAttributes
     );
   },
 
   *getSelectors(prefix, subtree, styles)
   {
     for (let element of this.getElements(prefix, subtree, styles))
-      yield [makeSelector(element, ""), element];
+      yield [makeSelector(element), element];
   },
 
   /**
    * Generator function returning selected elements.
    * @param {string} prefix the prefix for the selector.
    * @param {Node} subtree the subtree we work on.
    * @param {StringifiedStyle[]} styles the stringified style objects.
    */
@@ -306,17 +306,17 @@
 
 ContainsSelector.prototype = {
   requiresHiding: true,
   dependsOnCharacterData: true,
 
   *getSelectors(prefix, subtree, styles)
   {
     for (let element of this.getElements(prefix, subtree, styles))
-      yield [makeSelector(element, ""), subtree];
+      yield [makeSelector(element), subtree];
   },
 
   *getElements(prefix, subtree, styles)
   {
     let actualPrefix = (!prefix || incompletePrefixRegexp.test(prefix)) ?
         prefix + "*" : prefix;
 
     let elements = scopedQuerySelectorAll(subtree, actualPrefix);