Bug 89971 [Viewers] Viewers that use IViewerLabelProvider do too many instanceof checks
M6 Checking our viewer the calls to buildLabel are doing too many instanceof checks. As a result certain viewers (such as the table viewer) are twice as slow as they were in 3.0 due to these checks. I have written some performance suites to test the Table, Tree, List and Combo viewers. Table and Tree have this issue.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/StructuredViewer.java
* this method.
	 * </p>
	 * 
	 * @param element
	 *            the element
	 * @param item the item to unmap
	 * @since 2.0
	 */
	protected void unmapElement(Object element, Widget item) {
		
		
		if (elementMap != null && elementMap.get(element) == item) {
			
			unmapElement(element);
		}
	}
	/**
	 * Updates the given elements' presentation when one or more of their
	 * properties change. Only the given elements are updated.
	 * <p>
	 * This does not handle structural changes (e.g. addition or removal of
	 * elements), and does not update any other related elements (e.g. child
	 * elements). To handle structural changes, use the <code>refresh</code>
	 * methods instead.
	 * </p>
	 * <p>
	 * This should be called when an element has changed in the model, in order
	 * to have the viewer accurately reflect the model. This method only affects
	 * the viewer, not the model.
	 * </p>