Fix compilation against latest zest

Author: akurtakov

systemtap/org.eclipse.linuxtools.callgraph/src/org/eclipse/linuxtools/internal/callgraph/AggregateLayoutAlgorithm.java

@@ -25,7 +25,7 @@
  * Aggregate View. This avoids needing to design a Layout Algorithm
  * from scratch.
  */
-public class AggregateLayoutAlgorithm extends GridLayoutAlgorithm{
+public class AggregateLayoutAlgorithm extends GridLayoutAlgorithm.Zest1{
 
     private ArrayList<Long> list;
     private Long totalTime;