Bug 178519 Problems in multi-rows header
Please see the attachments.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/layout/pdf/PDFRowLM.java
{
		super( context, parent, content, executor );
		tbl = getTableLayoutManager( );
		calculateSpecifiedHeight( );
	}
	protected void calculateSpecifiedHeight( )
	{
		super.calculateSpecifiedHeight( );
		if ( specifiedHeight == 0 )
		{
			IStyle style = content.getComputedStyle( );
			int fontSize = getDimensionValue( style
					.getProperty( IStyle.STYLE_FONT_SIZE ) );
			specifiedHeight = fontSize;
		}
	}
	protected void createRoot( )
	{
		root = AreaFactory.createRowArea( (IRowContent) content );
	}
	protected void initialize( )
	{
		if ( root == null )
		{
			createRoot( );
		}
		maxAvaWidth = parent.getCurrentMaxContentWidth( );
		root.setWidth( getCurrentMaxContentWidth( ) );
		root.setAllocatedHeight( parent.getCurrentMaxContentHeight( ) );
		maxAvaHeight = root.getContentHeight( );