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
Widget w = findItem(elements[i]);
			if (w instanceof TableItem) {
				TableItem item = (TableItem) w;
				disassociate(item);
				indices[count++] = table.indexOf(item);
			}
		}
		if (count < indices.length) {
			System.arraycopy(indices, 0, indices = new int[count], 0, count);
		}
		table.remove(indices);
		
		
		if (table.getItemCount() == 0) {
			table.removeAll();
		}
	}
	/**
	 * Returns whether there is an active cell editor.
	 * 
	 * @return <code>true</code> if there is an active cell editor, and
	 *         <code>false</code> otherwise
	 */
	public boolean isCellEditorActive() {
		return tableViewerImpl.isCellEditorActive();
	}
	/**
	 * Removes the given elements from this table viewer. The selection is
	 * updated if required.
	 * <p>