Bug 174701 [Viewers] ViewerRow should be reused instead of connected to the Item
Currently we create a ViewerRow ver every Item we create this can degrade performance, we should cache the row and reuse it
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ViewerRow.java
*     Tom Shindl <tom.schindl@bestsolution.at> - initial API and implementation
 *                                                fix for bug 166346, bug 167325s
 *                                              - Fix for bug 174355
 ******************************************************************************/
package org.eclipse.jface.viewers;
import org.eclipse.jface.util.Policy;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.Font;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Item;
/**
 * ViewerRow is the abstract superclass of the part that represents items in a
 * Table or Tree.
 * 
 * @since 3.3 <strong>EXPERIMENTAL</strong> This class or interface has been
 *        added as part of a work in progress. This API may change at any given
 *        time. Please do not use this API without consulting with the
 *        Platform/UI team.
 * 
 */
public abstract class ViewerRow {
	/**
	 * Key used to reference ViewerRow in the widgets data-map
	 */
	public static final String ROWPART_KEY = Policy.JFACE + ".ROWPART"; 
	/**
	 * Constant denoting the row above the current one (value is 1).