window: Split search into words

Rather than using the search entry text as a single term when filtering
panels, split the text into multiple terms and require result to match all
of them, which is consistent with the search provider and the encouraged
search pattern for GNOME applications.

https://bugzilla.gnome.org/show_bug.cgi?id=694960

shell/cc-window.c

@@ -556,12 +556,24 @@ model_filter_func (GtkTreeModel    *model,
                    GtkTreeIter     *iter,
                    CcWindowPrivate *priv)
 {
+  char **terms, **t;
+  gboolean matches;
+
   if (!priv->filter_string)
     return FALSE;
 
-  return cc_shell_model_iter_matches_search (CC_SHELL_MODEL (model),
-                                             iter,
-                                             priv->filter_string);
+  terms = g_strsplit (priv->filter_string, " ", -1);
+  for (t = terms; *t; t++)
+    {
+      matches = cc_shell_model_iter_matches_search (CC_SHELL_MODEL (model),
+                                                    iter,
+                                                    *t);
+      if (!matches)
+        break;
+    }
+  g_strfreev (terms);
+
+  return matches;
 }
 
 static gboolean