Remove support for the obsolete <isindex> tag.

Source/devtools/front_end/ElementsTreeOutline.js

 /*
  * Copyright (C) 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2008 Matt Lilek <webkit@mattlilek.com>
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
@@ skipping 818 matching lines @@
     this._expandedChildrenLimit = WebInspector.ElementsTreeElement.InitialChildrenLimit;
 }
 
 WebInspector.ElementsTreeElement.InitialChildrenLimit = 500;
 
 // A union of HTML4 and HTML5-Draft elements that explicitly
 // or implicitly (for HTML5) forbid the closing tag.
 // FIXME: Revise once HTML5 Final is published.
 WebInspector.ElementsTreeElement.ForbiddenClosingTagElements = [
     "area", "base", "basefont", "br", "canvas", "col", "command", "embed", "frame",
-    "hr", "img", "input", "isindex", "keygen", "link", "meta", "param", "source"
+    "hr", "img", "input", "keygen", "link", "meta", "param", "source"
 ].keySet();
 
 // These tags we do not allow editing their tag name.
 WebInspector.ElementsTreeElement.EditTagBlacklist = [
     "html", "head", "body"
 ].keySet();
 
 WebInspector.ElementsTreeElement.prototype = {
     highlightSearchResults: function(searchQuery)
     {
@@ skipping 1788 matching lines @@
         var treeOutline = new WebInspector.ElementsTreeOutline(false, false);
         treeOutline.rootDOMNode = /** @type {!WebInspector.DOMNode} */ (object);
         treeOutline.element.classList.add("outline-disclosure");
         if (!treeOutline.children[0].hasChildren)
             treeOutline.element.classList.add("single-node");
         treeOutline.setVisible(true);
         treeOutline.element.treeElementForTest = treeOutline.children[0];
         return treeOutline.element;
     }
 }