Bug 40785 [plan item] Overview ruler improvements
- navigation from ruler to editor - hovering over header area shows number of errors/warning (header annotations in general)
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);
				}
			}
			/**
			 * @see IAnnotationModelListenerExtension#modelChanged(AnnotationModelEvent)
			 */
			public void modelChanged(AnnotationModelEvent event) {
				Object[] listeners= fListenerList.getListeners();
				for (int i= 0; i < listeners.length; i++) {
					Object curr= listeners[i];
					if (curr instanceof IAnnotationModelListenerExtension) {
						((IAnnotationModelListenerExtension) curr).modelChanged(event);
					}