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/AbstractTreeViewer.java
/**
	 * Constant indicating that all levels of the tree should be expanded or
	 * collapsed.
	 * 
	 * @see #expandToLevel(int)
	 * @see #collapseToLevel(Object, int)
	 */
	public static final int ALL_LEVELS = -1;
	/**
	 * List of registered tree listeners (element type:
	 * <code>TreeListener</code>).
	 */
	private ListenerList treeListeners = new ListenerList();
	/**
	 * The level to which the tree is automatically expanded each time the
	 * viewer's input is changed (that is, by <code>setInput</code>). A value
	 * of 0 means that auto-expand is off.
	 * 
	 * @see #setAutoExpandLevel
	 */
	private int expandToLevel = 0;
	/**
	 * Safe runnable used to update an item.
	 */
	class UpdateItemSafeRunnable extends SafeRunnable {