Currently, there is no way for windows in Chrome do not adhere to any aspect ratio. When showing content on windows that need to adhere to this, it is customary to use letterboxing or pillarboxing (i.e. black bars around video to preserve the clips original aspect ratio in film).
This change is meant to allow windows to be able to adhere to a certain aspect ratio to current and future views::Widgets.
Comment 1 by bugdroid1@chromium.org
, Jun 22 2018