NTP - Refactor the most visited code to uncouple it from the rest of the NTP....

chrome/browser/resources/shared/js/class_list.js

+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * @fileoverview This implements the HTML5 HTMLElement classList property.
+ */
+
+// TODO(arv): Remove this when classList is available in WebKit.
+// https://bugs.webkit.org/show_bug.cgi?id=20709
+
+if (typeof document.createElement('div').classList == 'undefined') {
+
+function DOMTokenList(el) {
+  this.el_ = el;
+}
+
+(function() {
+
+  var re = /\s+/;
+
+  function split(el) {
+    var cn = el.className.replace(/^\s+|\s$/g, '');
+    if (cn == '')
+      return [];
+    return cn.split(re);
+  }
+
+  function DOMException_(code) {
+    this.code = code;
+  }
+  DOMException_.prototype = DOMException.prototype;
+
+  function assertValidToken(s) {
+    if (s == '')
+      throw new DOMException_(DOMException.SYNTAX_ERR);
+    if (re.test(s))
+      throw new DOMException_(DOMException.INVALID_CHARACTER_ERR);
+  }
+
+  DOMTokenList.prototype = {
+    contains: function(token) {
+      assertValidToken(token);
+      return split(this.el_).indexOf(token) >= 0;
+    },
+    add: function(token) {
+      assertValidToken(token);
+      if (this.contains(token))
+        return;
+      var cn = this.el_.className;
+      this.el_.className += (cn == '' || re.test(cn.slice(-1)) ? '' : ' ') +
+          token;
+    },
+    remove: function(token) {
+      assertValidToken(token);
+      var names = split(this.el_);
+      var s = [];
+      for (var i = 0; i < names.length; i++) {
+        if (names[i] != token)
+          s.push(names[i])
+      }
+      this.el_.className = s.join(' ');
+    },
+    toggle: function(token) {
+      assertValidToken(token);
+      if (this.contains(token)) {
+        this.remove(token);
+        return false;
+      } else {
+        this.add(token);
+        return true;
+      }
+    },
+    get length() {
+      return split(this.el_).length;
+    },
+    item: function(index) {
+      return split(this.el_)[index];
+    }
+  };
+
+})();
+
+HTMLElement.prototype.__defineGetter__('classList', function() {
+  var tl = new DOMTokenList(this);
+  // Override so that we reuse the same DOMTokenList and so that
+  // el.classList == el.classList
+  this.__defineGetter__('classList', function() {
+    return tl;
+  });
+  return tl;
+});
+
+} // if