GitLab

This will allow features that use constrained windows (e.g. printing)
  work on all guest views: app-view/web-view/mime-handler-view, etc.

BUG=411765
Test=This is internal only for now, nothing visible,
  once the full support for printing and saving mime-handler-view lands
  it will be used.

Review URL: https://codereview.chromium.org/552013005

Cr-Commit-Position: refs/heads/master@{#293898}