Bug 41443 overview ruler not working
smoke test for 20030812 The overview ruler in the Java editor does not work when starting with a fresh workspace as described in the smoke test scenario.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
* @see org.eclipse.ui.texteditor.ITextEditorExtension3#isChangeInformationShowing()
	 */
	public boolean isChangeInformationShowing() {
		return fIsChangeInformationShown;
	}
	
	/**
	 * Creates a new <code>DocumentLineDiffer</code> and installs it with <code>model</code>.
	 * The default reference provider is installed with the newly created differ.
	 * 
	 * @param model the annotation model of the current document.
	 * @return a new <code>DocumentLineDiffer</code> instance.
	 * @since R3.0
	 */
	private DocumentLineDiffer createDiffer(IAnnotationModelExtension model) {
		DocumentLineDiffer differ;
		differ= new DocumentLineDiffer();
		IQuickDiffProviderImplementation provider= getDefaultReferenceProvider();
		if (provider != null)
			differ.setReferenceProvider(provider);
		model.addAnnotationModel(IChangeRulerColumn.QUICK_DIFF_MODEL_ID, differ);
		return differ;
	}
	
	/**
	 * Returns the default quick diff reference provider. It is determined by first trying to 
	 * enable the preferred provider as specified by the preferences; if this is unsuccessful, the
	 * default provider as specified by the extension point mechanism is installed. If that fails
	 * as well, <code>null</code> is returned.
	 *