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 Object getAnnotations(Position position) {
				return fReverseMap.get(position);
			}
						
			/*
			 * @see AnnotationModel#addAnnotation(Annotation, Position, boolean)
			 */
			protected void addAnnotation(Annotation annotation, Position position, boolean fireModelChanged) throws BadLocationException {
				super.addAnnotation(annotation, position, fireModelChanged);
				fCurrentEvent.annotationAdded(annotation);
				
				Object cached= fReverseMap.get(position);
				if (cached == null)
					fReverseMap.put(position, annotation);
				else if (cached instanceof List) {
					List list= (List) cached;
					list.add(annotation);
				} else if (cached instanceof Annotation) {
					List list= new ArrayList(2);
					list.add(cached);
					list.add(annotation);
					fReverseMap.put(position, list);
				}
			}
			
			/*
			 * @see AnnotationModel#removeAllAnnotations(boolean)
			 */
			protected void removeAllAnnotations(boolean fireModelChanged) {
				for (Iterator iter= getAnnotationIterator(); iter.hasNext();) {