Bug 36672 call hierarchy: Should show a progress bar
The Call Hierarchy view should show a progress bar when searching for callers/callees, allowing the user to abort the search.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/callhierarchy/CallHierarchyContentProvider.java
/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *   Jesper Kamstrup Linnet (eclipse@kamstrup-linnet.dk) - initial API and implementation 
 * 			(report 36180: Callers/Callees view)
 ******************************************************************************/
package org.eclipse.jdt.internal.ui.callhierarchy;
import org.eclipse.jface.viewers.ITreeContentProvider;
import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.jdt.core.IJavaElement;
import org.eclipse.jdt.internal.corext.callhierarchy.MethodWrapper;
public class CallHierarchyContentProvider implements ITreeContentProvider {
    private final static Object[] EMPTY_ARRAY = new Object[0];
    private TreeViewer fViewer;
    public CallHierarchyContentProvider() {
        super();
    }
    /**
     * @see org.eclipse.jface.viewers.ITreeContentProvider#getChildren(java.lang.Object)
     */
    public Object[] getChildren(Object parentElement) {
        if (parentElement instanceof TreeRoot) {
            TreeRoot dummyRoot = (TreeRoot) parentElement;