Merge "Make pane logic consistent with documentation" into tm-dev am: 9178d29c98 am: 6e79d68e24

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16943020

Change-Id: I57c542eb86dd1b56b2ef315485abec2f7f7a6ca3