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
break;
			}
			
			super.doOperation(operation);
		}
		
		public void insertTextConverter(ITextConverter textConverter, int index) {
			throw new UnsupportedOperationException();
		}
		
		public void addTextConverter(ITextConverter textConverter) {
			if (fTextConverters == null) {
				fTextConverters= new ArrayList(1);
				fTextConverters.add(textConverter);
			} else if (!fTextConverters.contains(textConverter))
				fTextConverters.add(textConverter);
		}
		
		public void removeTextConverter(ITextConverter textConverter) {
			if (fTextConverters != null) {
				fTextConverters.remove(textConverter);
				if (fTextConverters.size() == 0)
					fTextConverters= null;
			}
		}
		
		/*
		 * @see TextViewer#customizeDocumentCommand(DocumentCommand)
		 */
		protected void customizeDocumentCommand(DocumentCommand command) {