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

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

Index: chrome/browser/resources/shared/js/cr/ui/card_slider.js
diff --git a/chrome/browser/resources/shared/js/cr/ui/card_slider.js b/chrome/browser/resources/shared/js/cr/ui/card_slider.js
index cb04a3f14ce2971cfccccd5cd74c2b0b4747cb37..299004ebef6e273a96880729bb33a11db7fa1467 100644
--- a/chrome/browser/resources/shared/js/cr/ui/card_slider.js
+++ b/chrome/browser/resources/shared/js/cr/ui/card_slider.js
@@ -104,8 +104,10 @@ cr.define('cr.ui', function() {
     /**
      * 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.');
@@ -120,8 +122,10 @@ cr.define('cr.ui', function() {
       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));
 
@@ -236,9 +240,6 @@ cr.define('cr.ui', function() {
       if (e.wheelDeltaX == 0)
         return;
 
-      // Prevent OS X 10.7+ history swiping on the NTP.
-      e.preventDefault();

[Patrick Dubroy, 2012/04/17 17:28:24]

There's no need for this. It doesn't actually prevent the history swiping
anyways; just having *any* event handler for mousewheel will do that.

[Nico, 2012/04/17 23:22:35]

That used to be not true. Are you sure it's true now?

[Patrick Dubroy, 2012/04/18 14:43:06]

As mentioned above, you're right about preventDefault(). However, this code is
still unnecessary, because we don't want card sliding to take precedence over
history swiping, and anyways, this handler should never be called when history
swiping is enabled.

-
       // 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