Code review comment for lp:~manuel-nicetto/unity/bug-754565

+ bool _shift_pressed;

You are using tab here. Please, use spaces instead.

+ _shift_pressed=false;
+ _icon_mouse_down->_shift_pressed=_shift_pressed;

Use spaces before and after the assignment operator. Something like:
_shift_pressed = false;
_icon_mouse_down->_shift_pressed = _shift_pressed;