Fix shortcuts alignment in landscape

- Take left inset into account.
- If there is no way to orient the shortcuts next to the icon,
  instead center it in the drag layer and don't draw the arrow.
- If possible, place the shortcuts to the left or right of the
  icon when centered vertically. If for whatever reason that
  isn't possible, center the shortcuts horizontally as well.

Bug: 33421656
Change-Id: I838b30ea487e0f7c64637db1cb8991ca3ee16bf9