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
if (original == null)
			return null;
		CompilationUnitInfo cuInfo= (CompilationUnitInfo) info;
		setUpSynchronization(cuInfo);
		IProblemRequestor requestor= cuInfo.fModel instanceof IProblemRequestor ? (IProblemRequestor) cuInfo.fModel : null;
		if (requestor instanceof IProblemRequestorExtension) {
			IProblemRequestorExtension extension= (IProblemRequestorExtension) requestor;
			extension.setIsActive(false);
			extension.setIsHandlingTemporaryProblems(isHandlingTemporaryProblems());
		}
		if (JavaModelUtil.isPrimary(original))
			original.becomeWorkingCopy(requestor, getProgressMonitor());
		cuInfo.fCopy= original;
		if (cuInfo.fModel instanceof CompilationUnitAnnotationModel)   {
			CompilationUnitAnnotationModel model= (CompilationUnitAnnotationModel) cuInfo.fModel;
			model.setCompilationUnit(cuInfo.fCopy);
		}
		if (cuInfo.fModel != null)
			cuInfo.fModel.addAnnotationModelListener(fGlobalAnnotationModelListener);
		return cuInfo;
	}
	
	/**
	 * Creates a fake compilation unit.
	 *
	 * @param element the element
	 * @param setContents tells whether to read and set the contents to the new CU
	 * @since 3.2
	 */
	private ICompilationUnit createFakeCompiltationUnit(Object element, boolean setContents) {