Preview does not count in tirggering a form breakpoint

Problem/Motivation

Node form changes from two columns to single column at a certain breakpoint.

Preview panel reduced the width of the form, but does not affect the breakpoint. When visible area for the form is reduced to the breakpoint the css-breakpoint for the form should trigger.

Steps to reproduce

Edit content at 1000px viewport. Open preview at default width (which is about 50% of the viewpport)-

Proposed resolution

Count preview width to the breakpoint so that only the visible area counts. (similar to when core toolbar's horizontal menu is active)

Remaining tasks

User interface changes

API changes

Data model changes