Mac: Prevent NTP mousewheel events from being suppressed on Lion.

chrome/browser/resources/shared/js/cr/ui/card_slider.js

 // Copyright (c) 2012 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 Card slider implementation. Allows you to create interactions
  * that have items that can slide left to right to reveal additional items.
  * Works by adding the necessary event handlers to a specific DOM structure
  * including a frame, container and cards.
  * - The frame defines the boundary of one item. Each card will be expanded to
@@ skipping 86 matching lines @@
     /**
      * The current left offset of the container relative to the frame.
      * @type {number}
      * @private
      */
     currentLeft_: 0,
 
     /**
      * Initialize all elements and event handlers. Must call after construction
      * and before usage.
+     * @param {boolean} ignoreMouseWheelEvents If true, horizontal mouse wheel
+     *     events will be ignored, rather than flipping between pages.
      */
-    initialize: function() {
+    initialize: function(ignoreMouseWheelEvents) {
       var view = this.container_.ownerDocument.defaultView;
       assert(view.getComputedStyle(this.container_).display == '-webkit-box',
           'Container should be display -webkit-box.');
       assert(view.getComputedStyle(this.frame_).overflow == 'hidden',
           'Frame should be overflow hidden.');
       assert(view.getComputedStyle(this.container_).position == 'static',
           'Container should be position static.');
 
       this.updateCardWidths_();
 
       this.mouseWheelScrollAmount_ = 0;
       this.mouseWheelCardSelected_ = false;
       this.mouseWheelIsContinuous_ = false;
       this.scrollClearTimeout_ = null;
-      this.frame_.addEventListener('mousewheel',
-                                   this.onMouseWheel_.bind(this));
+      if (!ignoreMouseWheelEvents) {
+        this.frame_.addEventListener('mousewheel',
+                                     this.onMouseWheel_.bind(this));
+      }
       this.container_.addEventListener(
           'webkitTransitionEnd', this.onWebkitTransitionEnd_.bind(this));
 
       // Also support touch events in case a touch screen happens to be
       // available.  Ideally we would support touch events whenever they
       // are fired, but for now restrict this extra code to when we know
       // we want to support touch input.
       if (cr.isTouchOptimized) {
         var TouchHandler = cr.ui.TouchHandler;
         this.container_.addEventListener(TouchHandler.EventType.TOUCH_START,
@@ skipping 94 matching lines @@
     },
 
     /**
      * Handle horizontal scrolls to flip between pages.
      * @private
      */
     onMouseWheel_: function(e) {
       if (e.wheelDeltaX == 0)
         return;
 
-      // Prevent OS X 10.7+ history swiping on the NTP.
-      e.preventDefault();
-
       // Continuous devices such as an Apple Touchpad or Apple MagicMouse will
       // send arbitrary delta values. Conversly, standard mousewheels will
       // send delta values in increments of 120.  (There is of course a small
       // chance we mistake a continuous device for a non-continuous device.
       // Unfortunately there isn't a better way to do this until real touch
       // events are available to desktop clients.)
       var DISCRETE_DELTA = 120;
       if (e.wheelDeltaX % DISCRETE_DELTA)
         this.mouseWheelIsContinuous_ = true;
 
@@ skipping 362 matching lines @@
 
       // Ensure we're at a card bounary
       this.transformToCurrentCard_(true);
     },
   };
 
   return {
     CardSlider: CardSlider
   };
 });