Set css class on toolitems when a palette or toolbar popsdown

src/sugar3/graphics/palettewindow.py

@@ -1198,6 +1198,7 @@ class WidgetInvoker(Invoker):
 
         context = self.parent.get_style_context()
         context.add_class('toolitem')
+        context.add_class('palette-down')
 
         gap = _calculate_gap(self.get_rect(), palette.get_rect())
         if gap:

src/sugar3/graphics/toolbarbox.py

@@ -130,6 +130,7 @@ class ToolbarButton(ToolButton):
         alloc = self.get_allocation()
         context = self.get_style_context()
         context.add_class('toolitem')
+        context.add_class('toolbar-down')
         if not self.is_expanded() or self.props.palette is not None and \
                 self.props.palette.is_up():
             ToolButton.do_draw(self, cr)