Mouse release event ignored in popup menus on OS X (regression from Qt 4)

In Qt 5.3.1 when you hold down the mouse to open a popup menu, move the mouse over a menu entry and the release the mouse button the menu is closed but the menu action is not triggered.

See the attached simple test. Hold down the mouse over the button that says click me, a popup menu will open, now move your mouse to a menu button and release the mouse button. The menu closes but the action is not triggered.

Instead if you release the mouse once the menu has popped up and then click on the menu entries, they work (the text in the label is changed).

This is a regression from Qt 4, is inconsistent with how non Qt popup menus behave in OS X and makes popup menus much harder to use on OS X.