desks: Fix error in overview dragging with respect to desk bounds.

It was a clause that was always returning true, thus skipping the next
clause which happens only if:

1) User is in snapped splitview with desks.
2) User drags window on top of splitview window, up to the same side as
the desks bar, and then across to the desk bar (and reverse), almost
as if to intentionally avoid the desk bar.

With this CL, users who follow the above steps will get a slightly
better UX.

Test: manual
Bug: none
Change-Id: Ib7d352466fadaf4a61e3a0534c66982a42752380
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2057595
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741704}

ash/wm/overview/overview_window_drag_controller.cc

@@ -456,7 +456,7 @@ void OverviewWindowDragController::ContinueNormalDrag(
 
       float value = 0.f;
       if (centerpoint.y() < desks_bar_bounds_.y() ||
-          centerpoint.y() > desks_bar_bounds_.y()) {
+          centerpoint.y() > desks_bar_bounds_.bottom()) {
         // Coming vertically, this is the main use case. This is a ratio of the
         // distance from |centerpoint| to the closest edge of |desk_bar_bounds|
         // to the distance from |shrink_bounds| to |desk_bar_bounds|.