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/ColumnViewer.java
* 
	 * @return the number of columns
	 * 
	 * @since 3.3
	 */
	protected abstract int doGetColumnCount();
	/**
	 * Returns the label provider associated with the column at the given index
	 * or <code>null</code> if no column with this index is known.
	 * 
	 * @param columnIndex
	 *            the column index
	 * @return the label provider associated with the column or
	 *         <code>null</code> if no column with this index is known
	 * 
	 * @since 3.3
	 */
	public CellLabelProvider getLabelProvider(int columnIndex) {
		ViewerColumn column = getViewerColumn(columnIndex);
		if (column != null) {
			return column.getLabelProvider();
		}
		return null;
	}
	private void handleMouseDown(MouseEvent e) {
		ViewerCell cell = getCell(new Point(e.x, e.y));
		if (cell != null) {
			triggerEditorActivationEvent(new ColumnViewerEditorActivationEvent(
					cell, e));
		}