Repro steps are simply
1. On desktop mode, right click on shelf and set position to left/right
2. Flip device (Eve) into tablet mode
No display settings were changed.

For a quick fix, reset display scale to default.

ctrl-shift-0.

This is happening because:
 -  We tell AppListView "is_side_shelf_" when the view is constructed.
 -  We (incorrectly)assume that changing the shelf orientation will close the AppListView, and is_side_shelf_ will not change for the lifetime of AppListView.
 - Homecher transition occurs when we go to tablet mode, this does not re-construct the AppListView, and the shelf shifts to the bottom of the screen while AppListView believes it is still on the side.

This is likely an old bug, but now that we support display scale it has become more obvious.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d36b6e27f338bfb6351d69136de58648e68043ac

commit d36b6e27f338bfb6351d69136de58648e68043ac
Author: Alex Newcomer <newcomer@chromium.org>
Date: Wed Jan 09 18:19:12 2019

cros: updating side shelf on tablet mode

Bottom shelf is enforced in tablet mode. AppListView didn't know this,
which led to some layout errors / overlapping components.

No need to update |is_side_shelf_| when tablet mode starts because
AppListView is destroyed when transitioning from tablet -> clamshell.

If this changes in the future, we should just ask the delegate for
shelf orientation. For now this is not necessary though.

BUG:  916601 
Change-Id: Iadab2b003c268501bd6ab44acec7f7a7e9cd97ee
Reviewed-on: https://chromium-review.googlesource.com/c/1388660
Reviewed-by: Weidong Guo <weidongg@chromium.org>
Commit-Queue: Alex Newcomer <newcomer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621225}
[modify] https://crrev.com/d36b6e27f338bfb6351d69136de58648e68043ac/ash/app_list/views/app_list_view.cc