Use a specialized new tab page in TOUCH_UI builds

chrome/browser/resources/touch_ntp/eventtracker.js

+// Copyright (c) 2011 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 EventTracker is a simple class that manages the addition and
+ *  removal of DOM event listeners.  In particular, it keeps track of all
+ *  listeners that have been added and makes it easy to remove some or all of
+ *  them without requiring all the information again.  This is particularly
+ *  handy when the listener is a generated function such as a lambda or the
+ *  result of calling Function.bind.  The goal of this class is to make it
+ *  easier to avoid memory leaks caused by DOM<->JS cycles - removing event
+ *  listeners breakes the DOM->JS part of the cycle.
+ */
+
+// Use an anonymous function to enable strict mode just for this file (which
+// will be concatenated with other files when embedded in Chrome)
+var EventTracker = (function() {
+  'use strict';
+
+  /**
+   *  Create an EventTracker to track a set of events.
+   *  EventTracker instances are typically tied 1:1 with other objects or
+   *  DOM elements whose listeners should be removed when the object is disposed
+   *  or the corresponding elements are removed from the DOM.
+   *  @constructor
+   */
+  function EventTracker() {
+    /**
+     *  @type {Array.<EventTracker.Entry>}
+     *  @private
+     */
+    this.listeners_ = [];
+  }
+
+  /**
+   * The type of the internal tracking entry.
+   *  @typedef {{node: !Node,
+   *            eventType: string,
+   *            listener: Function,
+   *            capture: boolean}}
+   */
+  EventTracker.Entry;
+
+  EventTracker.prototype = {
+    /**
+     * Add an event listener - replacement for Node.addEventListener.
+     * @param {!Node} node The DOM node to add a listener to.
+     * @param {string} eventType The type of event to subscribe to.
+     * @param {Function} listener The listener to add.
+     * @param {boolean} capture Whether to invoke during the capture phase.
+     */
+    add: function(node, eventType, listener, capture) {
+      var h = {
+        node: node,
+        eventType: eventType,
+        listener: listener,
+        capture: capture
+      };
+      this.listeners_.push(h);
+      node.addEventListener(eventType, listener, capture);
+    },
+
+    /**
+     * Remove any specified event listeners added with this EventTracker.
+     * @param {!Node} node The DOM node to remove a listener from.
+     * @param {string} eventType The type of event to remove.
+     */
+    remove: function(node, eventType) {
+      this.listeners_ = this.listeners_.filter(function(h) {
+        if (h.node == node && h.eventType == eventType) {
+          EventTracker.removeEventListener_(h);
+          return false;
+        }
+        return true;
+      });
+    },
+
+    /**
+     * Remove all event listeners added with this EventTracker.
+     */
+    removeAll: function() {
+      this.listeners_.forEach(EventTracker.removeEventListener_);
+      this.listeners_ = [];
+    }
+  };
+
+  /**
+   * Remove a single event listener given it's tracker entry.  It's up to the
+   * caller to ensure the entry is removed from listeners_.
+   * @param {EventTracker.Entry} h The entry describing the listener to remove.
+   * @private
+   */
+  EventTracker.removeEventListener_ = function(h) {
+    h.node.removeEventListener(h.eventType, h.listener, h.capture);
+  };
+
+  return EventTracker;
+})();
+