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
* 
	 * @since 2.0
	 */
	protected void internalRefresh(Object element, boolean updateLabels) {
		internalRefresh(element);
	}
	/**
	 * Adds the element item pair to the element map.
	 * <p>
	 * This method is internal to the framework; subclassers should not call
	 * this method.
	 * </p>
	 * 
	 * @param element
	 *            the element
	 * @param item
	 *            the corresponding widget
	 */
	protected void mapElement(Object element, Widget item) {
		if (elementMap != null)
			elementMap.put(element, item);
	}
	/**
	 * Determines whether a change to the given property of the given element
	 * would require refiltering and/or resorting.
	 * <p>
	 * This method is internal to the framework; subclassers should not call
	 * this method.
	 * </p>
	 *