Bug 201906 [Viewers] 3.4 ColumnViewerEditor leaks ViewerCell instances.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ColumnViewerEditor.java
* per cell-editor using {@link CellEditor#getDoubleClickTimeout()}
	 */
	public static final int KEEP_EDITOR_ON_DOUBLE_CLICK = 1 << 6;
	private int feature;
	/**
	 * @param viewer
	 *            the viewer this editor is attached to
	 * @param editorActivationStrategy
	 *            the strategy used to decide about editor activation
	 * @param feature
	 *            bit mask controlling the editor
	 *            <ul>
	 *            <li>{@link ColumnViewerEditor#DEFAULT}</li>
	 *            <li>{@link ColumnViewerEditor#TABBING_CYCLE_IN_ROW}</li>
	 *            <li>{@link ColumnViewerEditor#TABBING_HORIZONTAL}</li>
	 *            <li>{@link ColumnViewerEditor#TABBING_MOVE_TO_ROW_NEIGHBOR}</li>
	 *            <li>{@link ColumnViewerEditor#TABBING_VERTICAL}</li>
	 *            </ul>
	 */
	protected ColumnViewerEditor(ColumnViewer viewer,
			ColumnViewerEditorActivationStrategy editorActivationStrategy,
			int feature) {
		this.viewer = viewer;
		this.editorActivationStrategy = editorActivationStrategy;
		if ((feature & KEYBOARD_ACTIVATION) == KEYBOARD_ACTIVATION) {
			this.editorActivationStrategy
					.setEnableEditorActivationWithKeyboard(true);
		}
		this.feature = feature;
		initCellEditorListener();