Bug 155766 [Regression]Preview will not refresh the modify in design report
Details: Preview will not refresh the modify in design report Step: 1.New a report design. 2.New a label and input label1. 3.Preview. 4.Switch to Layout and modify the content of label as label2. 5.Preview. Actual result: It preview as "label1" twice. Exception result: Preview "label2" at the second time
viewer/org.eclipse.birt.report.viewer/src/org/eclipse/birt/report/viewer/utilities/WebViewer.java
* PDF format name
	 */
	final public static String PDF = "pdf"; 
	/**
	 * Birt web viewer plugin id
	 */
	final public static String WebAppPlugin = ViewerPlugin.PLUGIN_ID;
	/**
	 * locale preference name
	 */
	final public static String USER_LOCALE = "user_locale"; 
	/**
	 * Preference key for SVG chart flag.
	 */
	final public static String SVG_FLAG = "svg_flag"; 
	/**
	 * Preference key for master page content flag.
	 */
	final public static String MASTER_PAGE_CONTENT = "master_page_content"; 
	
	final public static String PREVIEW_MAXROW = "preview_maxrow"; 
	
	/**
	 * Key to indicate the format of the preview.
	 */
	public final static String FORMAT_KEY = "FORMAT_KEY"; 
	/**
	 * Key to indicate the 'allowPage' control of the preview.
	 */
	public final static String ALLOW_PAGE_KEY = "ALLOW_PAGE_KEY";