Perforamce:

do not bother to check if need to expand for
    strings that do not have $


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@448379 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/PropertyHelper.java

@@ -249,8 +249,8 @@ public class PropertyHelper {
      */
     public String replaceProperties(String ns, String value, Hashtable keys)
             throws BuildException {
-        if (value == null) {
-            return null;
+        if (value == null || value.indexOf('$') == -1) {
+            return value;
         }
         Vector fragments = new Vector();
         Vector propertyRefs = new Vector();