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
* The default implementation of this method tries first to find the widget
	 * for the given element assuming that it is the viewer's input; this is
	 * done by calling <code>doFindInputItem</code>. If it is not found
	 * there, it is looked up in the internal element map provided that this
	 * feature has been enabled. If the element map is disabled, the widget is
	 * found via <code>doFindInputItem</code>.
	 * </p>
	 * 
	 * @param element
	 *            the element
	 * @return the corresponding widget, or <code>null</code> if none
	 */
	protected final Widget findItem(Object element) {
		Widget result = doFindInputItem(element);
		if (result != null)
			return result;
		
		if (elementMap != null)
			return (Widget) elementMap.get(element);
		return doFindItem(element);
	}
	/**
	 * Notifies any double-click listeners that a double-click has been
	 * received. Only listeners registered at the time this method is called are
	 * notified.
	 * 
	 * @param event
	 *            a double-click event
	 * 
	 * @see IDoubleClickListener#doubleClick