Bug 19275 editor: context menu slow on large files
F2 it's slow, but only the first time after a change. then it's fast afain you make another change - it's slow again
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/compare/JavaHistoryEditorAction.java
/*******************************************************************************
 * Copyright (c) 2002 International Business Machines Corp. and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v0.5 
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v05.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 ******************************************************************************/
package org.eclipse.jdt.internal.ui.compare;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.StructuredSelection;
import org.eclipse.jface.action.Action;
import org.eclipse.jface.util.Assert;
import org.eclipse.ui.IActionDelegate;
import org.eclipse.ui.texteditor.IUpdate;
import org.eclipse.jdt.core.IJavaElement;
import org.eclipse.jdt.core.JavaModelException;
import org.eclipse.jdt.internal.ui.javaeditor.JavaEditor;
import org.eclipse.jdt.internal.ui.actions.SelectionConverter;
/**
 * A special action that makes JavaHistryAction available inside a text editor.
 */
public class JavaHistoryEditorAction extends Action implements IUpdate {