Problem/Motivation
Currently the overlay has a simple method for displacing itself to accomodate page elements at its edges. This method was sufficient for Drupal 7, but we find that more and more in Drupal 8, we need a more refined interface for placing and sizing the overlay.
Proposed resolution
Provide methods and events on the Drupal.overlay object that allow modules to suggest placement and sizing of the overlay on a given page.
Provide methods for modules to query the overlay's current sizing and position to determine if it needs to be moved or resized.
Remaining tasks
Propose an initial patch.
User interface changes
No visual UI changes.
API changes
Several changes, to be determined.