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
if (fProgressMonitor != null && fProgressMonitor.isCanceled())
					return;
					
				
				boolean isCanceled= false;
				boolean temporaryProblemsChanged= false;
				
				synchronized (fAnnotations) {
					
					fPreviouslyOverlaid= fCurrentlyOverlaid;
					fCurrentlyOverlaid= new ArrayList();
					if (fGeneratedAnnotations.size() > 0) {
						temporaryProblemsChanged= true;	
						removeAnnotations(fGeneratedAnnotations, false, true);
						fGeneratedAnnotations.clear();
					}
					
					if (fCollectedProblems != null && fCollectedProblems.size() > 0) {
						
						ICompilationUnit cu= getWorkingCopy(fInput);
						Iterator e= fCollectedProblems.iterator();
						while (e.hasNext()) {
							
							IProblem problem= (IProblem) e.next();
							
							if (fProgressMonitor != null && fProgressMonitor.isCanceled()) {
								isCanceled= true;
								break;
							}