Merge "Center drop target icons in landscape mode." into sc-dev am: 3287dd9fa7 am: d417d36615 am: b75ab0890a

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14980961

Change-Id: Idb48fdd39fa66d7a7813bcd61477cb0de10399cc