Merge "Respect aspect ratio restrictions in split screen and show letterbox...

Merge "Respect aspect ratio restrictions in split screen and show letterbox surfaces." into sc-dev am: 19c430b1 am: 63c029a5

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/14468599

Change-Id: If38a9ee873339ba25e8f93d0086c29b35511b288