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
* <p>
	 * Subclasses do not typically override this method, but implement
	 * <code>getSelectionFromWidget(List)</code> instead.
	 * <p>
	 * @return ISelection
	 */
	public ISelection getSelection() {
		Control control = getControl();
		if (control == null || control.isDisposed()) {
			return StructuredSelection.EMPTY;
		}
		List list = getSelectionFromWidget();
		return new StructuredSelection(list);
	}
	/**
	 * Retrieves the selection, as a <code>List</code>, from the underlying
	 * widget.
	 * 
	 * @return the list of selected elements
	 */
	protected abstract List getSelectionFromWidget();
	/**
	 * Returns the sorted and filtered set of children of the given element. The
	 * resulting array must not be modified, as it may come directly from the
	 * model's internal state.
	 * 
	 * @param parent
	 *            the parent element
	 * @return a sorted and filtered array of child elements
	 */