This patch should resolve an issue where the popupmenu for a combobox
could become 'stranded' if the plugin window was moved while the box was
open.

This change makes heavyweight views listen to window events from higher
in the window hierarchy. If a move or resize event from higher in the
hierarchy is encountered, blocking modal components will be dismissed.

This patch should resolve an issue where the popupmenu for a combobox
could become 'stranded' if the plugin window was moved while the box was
open.

This change will make plugin views (and other heavyweight views) listen
to their containing window, and dismiss any blocking modal components,
such as PopupMenus when the window is moved or resized.

This should fix issues where opening a combobox then moving the plugin
window could leave the combobox's popupmenu 'stranded'.

This behaviour was already present on windows, so this patch updates
Linux and macOS window-handling to match.

This reverts commit a6217ae9fb.