Loading a blend file can sometimes make the system look unresponsive. If there is a menu up at the time (like if you select from File/Recent) it will remain frozen onscreen until the file is loaded:
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Although the mouse cursor initially changes to a "wait" cursor, this is reset back to a normal pointer very early on in the process. These things both make the program look like it is hung. And not in a good way.
This patch just removes any menus that might be showing, and also ensures that the "waiting" mouse cursor continues to show until (almost) the end.
This is a subset of D10484. It makes sense that we might debate whether or not we want a "loading" dialog and what it might look like, but that can be separate from this.