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
* Signals the end of problem reporting.
			 */
			private void reportProblems(List reportedProblems) {
				if (fProgressMonitor != null && fProgressMonitor.isCanceled())
					return;
				boolean temporaryProblemsChanged= false;
				synchronized (getLockObject()) {
					boolean isCanceled= false;
					fPreviouslyOverlaid= fCurrentlyOverlaid;
					fCurrentlyOverlaid= new ArrayList();
					if (fGeneratedAnnotations.size() > 0) {
						temporaryProblemsChanged= true;
						removeAnnotations(fGeneratedAnnotations, false, true);
						fGeneratedAnnotations.clear();
					}
					if (reportedProblems != null && reportedProblems.size() > 0) {
						Iterator e= reportedProblems.iterator();
						while (e.hasNext()) {
							if (fProgressMonitor != null && fProgressMonitor.isCanceled()) {
								isCanceled= true;
								break;
							}
							IProblem problem= (IProblem) e.next();
							Position position= createPositionFromProblem(problem);
							if (position != null) {
								try {
									ProblemAnnotation annotation= new ProblemAnnotation(problem, fCompilationUnit);
									overlayMarkers(position, annotation);
									addAnnotation(annotation, position, false);
									fGeneratedAnnotations.add(annotation);