OngoingFactEntry: add dedicated style-class

This is a backport of ``4e2827c581a0c93b62aa021d8acd3aac25d25c36``.
All credit goes to (@camlafit).

Ref.:i#111

Author: elbenfreund

extension/widgets/ongoingFactEntry.js

@@ -48,7 +48,8 @@ var OngoingFactEntry = new Lang.Class({
             name: 'searchEntry',
             can_focus: true,
             track_hover: true,
-            hint_text: _("Enter activity...")
+            hint_text: _("Enter activity..."),
+            style_class: "search-entry"
         });
 
         this._controller = controller;