osdWindow: Use float values as input for osdWindow

Using the same type/interval as BarLevel means we can cut out the intermediate
LevelBar class in a follow-up cleanup.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/385

js/ui/shellDBus.js

@@ -94,6 +94,12 @@ var GnomeShell = class {
         if (serializedIcon)
             icon = Gio.Icon.new_for_string(serializedIcon);
 
+        // Translate from percentages in the D-Bus API to floats
+        if (!isNaN(level))
+            level /= 100;
+        if (!isNaN(maxLevel))
+            maxLevel /= 100;
+
         Main.osdWindowManager.show(monitorIndex, icon, label, level, maxLevel);
     }