Removed IUndoContext from adapters
diff --git a/plugins/org.eclipse.graphiti.ui/src/org/eclipse/graphiti/ui/editor/DiagramEditor.java b/plugins/org.eclipse.graphiti.ui/src/org/eclipse/graphiti/ui/editor/DiagramEditor.java
index 750c87d..3180a1b 100644
--- a/plugins/org.eclipse.graphiti.ui/src/org/eclipse/graphiti/ui/editor/DiagramEditor.java
+++ b/plugins/org.eclipse.graphiti.ui/src/org/eclipse/graphiti/ui/editor/DiagramEditor.java
@@ -31,7 +31,6 @@
 import java.util.List;
 import java.util.Map;
 
-import org.eclipse.core.commands.operations.IUndoContext;
 import org.eclipse.core.runtime.Assert;
 import org.eclipse.core.runtime.IProgressMonitor;
 import org.eclipse.draw2d.FigureCanvas;
@@ -46,7 +45,6 @@
 import org.eclipse.emf.edit.domain.IEditingDomainProvider;
 import org.eclipse.emf.transaction.RecordingCommand;
 import org.eclipse.emf.transaction.TransactionalEditingDomain;
-import org.eclipse.emf.workspace.IWorkspaceCommandStack;
 import org.eclipse.gef.ContextMenuProvider;
 import org.eclipse.gef.DefaultEditDomain;
 import org.eclipse.gef.EditPart;
@@ -813,10 +811,6 @@
 			}
 			return null; // not yet initialized
 		}
-		if (type == IUndoContext.class) {
-			// TODO ? Do we need to provide this ?
-			return ((IWorkspaceCommandStack) getEditingDomain().getCommandStack()).getDefaultUndoContext();
-		}
 		if (type == Diagram.class) {
 			return getDiagramTypeProvider().getDiagram();
 		}