Fixed RT-16364: TextArea: focus is not gained by clicking on empty area

diff -r a6ccbd21a7e4 -r 2c3c5712fec3 javafx-ui-controls/src/com/sun/javafx/scene/control/skin/TextAreaSkin.java
--- a/javafx-ui-controls/src/com/sun/javafx/scene/control/skin/TextAreaSkin.java	Tue Sep 06 09:41:01 2011 -0700
+++ b/javafx-ui-controls/src/com/sun/javafx/scene/control/skin/TextAreaSkin.java	Tue Sep 06 11:38:48 2011 -0700
@@ -131,7 +131,7 @@
 
             prefHeight += padding.getTop() + padding.getBottom();
 
-            return prefHeight;
+            return Math.max(prefHeight, scrollPane.getPrefViewportHeight());
         }
 
         @Override