Add scroll threshold for app list for mouse wheel events.

ui/app_list/pagination_controller.cc

Index: ui/app_list/pagination_controller.cc
diff --git a/ui/app_list/pagination_controller.cc b/ui/app_list/pagination_controller.cc
index 26494eb24a18901b59922f0ee9bb5efe91cf0dd5..c9081c4f1f6e043d6673ebdfaf0229c4a0c263e3 100644
--- a/ui/app_list/pagination_controller.cc
+++ b/ui/app_list/pagination_controller.cc
@@ -39,10 +39,8 @@ bool PaginationController::OnScroll(const gfx::Vector2d& offset,
     offset_magnitude = offset.y();
   }
 
-  // Do not scroll on very small touchpad events. Mouse wheel events should
-  // scroll, no matter how small the value change.
-  if (type == SCROLL_MOUSE_WHEEL ||
-      abs(offset_magnitude) > kMinScrollToSwitchPage) {
+  // Do not scroll on very small events.

[Matt Giuca, 2016/06/02 08:44:18]

// TODO(calamity): Something something https://crbug.com/594264.

[calamity, 2016/06/03 01:25:45]

Done.

+  if (abs(offset_magnitude) > kMinScrollToSwitchPage) {
     if (!pagination_model_->has_transition()) {
       pagination_model_->SelectPageRelative(offset_magnitude > 0 ? -1 : 1,
                                             true);