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
fList.clear();
			}
		}
		/**
		 * Annotation model dealing with java marker annotations and temporary problems.
		 * Also acts as problem requester for its compilation unit. Initially inactive. Must explicitly be
		 * activated.
		 */
		protected static class CompilationUnitAnnotationModel extends ResourceMarkerAnnotationModel implements IProblemRequestor, IProblemRequestorExtension {
			private static class ProblemRequestorState {
				boolean fInsideReportingSequence= false;
				List fReportedProblems;
			}
			private ThreadLocal fProblemRequestorState= new ThreadLocal();
			private int fStateCount= 0;
			private ICompilationUnit fCompilationUnit;
			private List fGeneratedAnnotations;
			private IProgressMonitor fProgressMonitor;
			private boolean fIsActive= false;
			private boolean fIsHandlingTemporaryProblems;
			private ReverseMap fReverseMap= new ReverseMap();
			private List fPreviouslyOverlaid= null;
			private List fCurrentlyOverlaid= new ArrayList();
			public CompilationUnitAnnotationModel(IResource resource) {
				super(resource);
			}
			public void setCompilationUnit(ICompilationUnit unit)  {
				fCompilationUnit= unit;
			}
			protected MarkerAnnotation createMarkerAnnotation(IMarker marker) {