Menu selection no longer works as expected

Interactions with menus have changed with qt-dev

What I am trying:

I open Qt Creator and click-and-hold on the "File" menu entry. Now I drag down the mouse while keeping the mouse button pressed and release the mouse button when over "New File or Project".

Expected behavior:
The new file or project dialog pops up. This happens with Qt 5.4.x.

Actual behavior:
The menu closes, nothing is triggered. This happens with Qt from the dev branch.

Clicking-and-releasing the "File" menu entry to open the menu and then clicking-and-releasing "New file or project" works in both versions.

Both versions also look identically when click-dragging, the new one just will never trigger the action that is selected.

Please fix this regression, it drives me crazy