Bug 40788 [plan item] Configurable Next/Previous actions
Toolbar drop down, or editor specific control. Needs to be coordinated with Platform UI.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
fIsChangeInformationShown= true;
				showLineNumberRuler();
			}
		} else 
			showChangeRuler(true);
	}
	/*
	 * @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;