Bug 201906 [Viewers] 3.4 ColumnViewerEditor leaks ViewerCell instances.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ColumnViewerEditor.java
private boolean inEditorDeactivation;
	/**
	 * Tabbing from cell to cell is turned off
	 */
	public static final int DEFAULT = 1;
	/**
	 * Should if the end of the row is reach started from the start/end of the
	 * row below/above
	 */
	public static final int TABBING_MOVE_TO_ROW_NEIGHBOR = 1 << 1;
	/**
	 * Should if the end of the row is reach started from the beginning in the
	 * same row
	 */
	public static final int TABBING_CYCLE_IN_ROW = 1 << 2;
	/**
	 * Support tabbing to Cell above/below the current cell
	 */
	public static final int TABBING_VERTICAL = 1 << 3;
	/**
	 * Should tabbing from column to column with in one row be supported
	 */
	public static final int TABBING_HORIZONTAL = 1 << 4;
	/**
	 * Style mask used to enable keyboard activation
	 */
	public static final int KEYBOARD_ACTIVATION = 1 << 5;
	/**
	 * Style mask used to turn <b>off</b> the feature that an editor activation
	 * is canceled on double click. It is also possible to turn off this feature