Bug 54900 [rulers] Java Editor does not show ruler on external Java files
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitDocumentProvider.java
private ListenerList fListenerList;
			public GlobalAnnotationModelListener() {
				fListenerList= new ListenerList();
			}
			/**
			 * @see IAnnotationModelListener#modelChanged(IAnnotationModel)
			 */
			public void modelChanged(IAnnotationModel model) {
				Object[] listeners= fListenerList.getListeners();
				for (int i= 0; i < listeners.length; i++) {
					((IAnnotationModelListener) listeners[i]).modelChanged(model);
				}
			}
			/**