Bug 28698 Ctrl+O (show outline) does not work if the file being shown in the editor is read only
M4 The summary tells all. Works if the file is not read only. Is this by design?
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitEditor.java
IWorkingCopyManager manager= JavaPlugin.getDefault().getWorkingCopyManager();
		ICompilationUnit unit= manager.getWorkingCopy(getEditorInput());
		
		if (unit != null) {
			try {
				if (reconcile) {
					synchronized (unit) {
						unit.reconcile();
					}
					return unit.getElementAt(offset);
				} else if (unit.isConsistent())
					return unit.getElementAt(offset);
					
			} catch (JavaModelException x) {
				JavaPlugin.log(x.getStatus());
				
			}
		}
		
		return null;
	}
	
	/*
	 * @see JavaEditor#getCorrespondingElement(IJavaElement)
	 */
	protected IJavaElement getCorrespondingElement(IJavaElement element) {
		try {
			return EditorUtility.getWorkingCopy(element, true);
		} catch (JavaModelException x) {
			JavaPlugin.log(x.getStatus());