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/TableViewer.java
* cell editor are lost.
	 */
	public void cancelEditing() {
		tableViewerImpl.cancelEditing();
	}
	/*
	 *  (non-Javadoc)
	 * @see org.eclipse.jface.viewers.StructuredViewer#doFindInputItem(java.lang.Object)
	 */
	protected Widget doFindInputItem(Object element) {
		if (equals(element, getRoot()))
			return getTable();
		return null;
	}
	/*
	 *  (non-Javadoc)
	 * @see org.eclipse.jface.viewers.StructuredViewer#doFindItem(java.lang.Object)
	 */
	protected Widget doFindItem(Object element) {
		
		TableItem[] children = table.getItems();
		for (int i = 0; i < children.length; i++) {
			TableItem item = children[i];
			Object data = item.getData();
			if (data != null && equals(data, element))
				return item;
		}
		return null;
	}
	/*