Make app list ContentsView scroll vertically in experimental app list.

This CL makes the app list contents view scroll vertically for the
experimental app list rather than horiztonally.

BUG=406222

Review URL: https://codereview.chromium.org/504033002

Cr-Commit-Position: refs/heads/master@{#291854}

ui/app_list/views/contents_view.cc

@@ -215,23 +215,13 @@ void ContentsView::UpdatePageBounds() {
   gfx::Rect outgoing_target(rect);
   int dir = target_page > current_page ? -1 : 1;
 
-  if (app_list::switches::IsExperimentalAppListEnabled()) {
-    // The experimental app list transitions horizontally.
-    int page_width = rect.width();
-    int transition_offset = progress * page_width * dir;
-
-    outgoing_target.set_x(transition_offset);
-    incoming_target.set_x(dir < 0 ? transition_offset + page_width
-                                  : transition_offset - page_width);
-  } else {
-    // The normal app list transitions vertically.
+  // Pages transition vertically.
   int page_height = rect.height();
   int transition_offset = progress * page_height * dir;
 
   outgoing_target.set_y(transition_offset);
   incoming_target.set_y(dir < 0 ? transition_offset + page_height
                                 : transition_offset - page_height);
-  }
 
   view_model_->view_at(current_page)->SetBoundsRect(outgoing_target);
   view_model_->view_at(target_page)->SetBoundsRect(incoming_target);