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
fPropertyListener= new IPropertyChangeListener() {
			public void propertyChange(PropertyChangeEvent event) {
				if (HANDLE_TEMPORARY_PROBLEMS.equals(event.getProperty()))
					enableHandlingTemporaryProblems();
			}
		};
		
		fGlobalAnnotationModelListener= new GlobalAnnotationModelListener();
		
		JavaPlugin.getDefault().getPreferenceStore().addPropertyChangeListener(fPropertyListener);
	}
	
	/**
	 * Creates a compilation unit from the given file.
	 * 
	 * @param file the file from which to create the compilation unit
	 */
	protected ICompilationUnit createCompilationUnit(IFile file) {
		Object element= JavaCore.create(file);
		if (element instanceof ICompilationUnit)
			return (ICompilationUnit) element;
		return null;
	}
	/*
	 * @see AbstractDocumentProvider#createElementInfo(Object)
	 */
	protected ElementInfo createElementInfo(Object element) throws CoreException {
		
		if ( !(element instanceof IFileEditorInput))
			return super.createElementInfo(element);