Usage of the tray widget to display activity icons

ActivitiesBox patch for ticket #2713.

sugar/graphics/Makefile.am

@@ -22,5 +22,6 @@ sugar_PYTHON =			\
 	toolbox.py		\
 	toolbutton.py		\
 	toolcombobox.py		\
+	tray.py			\
 	window.py		\
 	xocolor.py

sugar/graphics/tray.py

@@ -111,8 +111,12 @@ class HTray(gtk.HBox):
         self._viewport.traybar.insert(item, index)
 
     def remove_item(self, index):
+        item = self._viewport.traybar.get_nth_item(index)
         self._viewport.traybar.remove(item)
 
+    def get_item_index(self, item):
+        return self._viewport.traybar.get_item_index(item)
+
 class TrayButton(ToolButton):
     def __init__(self, **kwargs):
         ToolButton.__init__(self, **kwargs)