Bug 168305 IsHostPage doesn't work for birt:report tag.[0603]
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/taglib/AbstractViewerTag.java
protected boolean __validateViewerId( )
	{
		Pattern p = Pattern.compile( "^\\w+$" ); 
		Matcher m = p.matcher( viewer.getId( ) );
		return m.find( );
	}
	/**
	 * Handle event before doEndTag
	 */
	protected void __beforeEndTag( )
	{
		super.__beforeEndTag( );
		viewer.setParameters( parameters );
		
		pageContext.setAttribute( viewer.getId( ), viewer.getId( ) );
	}
	/**
	 * Handle use IFrame to preview report. Each IFrame should have an unique
	 * id.
	 * 
	 * @param src
	 * @param target
	 * @throws Exception
	 */
	protected void __handleIFrame( String src, String target ) throws Exception
	{
		JspWriter writer = pageContext.getOut( );
		writer.write( "<script type=\"text/javascript\">\n" ); 
		writer.write( "function loadViewer" + viewer.getId( ) + "(){\n" ); 
		writer.write( "var divObj = document.createElement( \"DIV\" );\n" );