The test  test/java/awt/Mouse/MouseDragEvent/MouseDraggedTest.java fails on Linux for extra mouse buttons.

This is because Xsystem is not set state for the extra button event.
See the comment for the XWindow.handleMotionNotify(XEvent) method:
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        //this doesn't work for extra buttons because Xsystem is sending state==0 for every extra button event.
        // we can't correct it in MouseEvent class as we done it with modifiers, because exact type (DRAG|MOVE)
        // should be passed from XWindow.
        final int buttonsNumber = XToolkit.getNumberOfButtonsForMask();

        for (int i = 0; i < buttonsNumber; i++){
            // TODO : here is the bug in WM: extra buttons doesn't have state!=0 as they should.
            if ((i != 4) && (i != 5)) {
                mouseKeyState = mouseKeyState | (xme.get_state() & XlibUtil.getButtonMask(i + 1));
            }
        }
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