Bug 163360 [Field Assist] - API - Provide ControlDecoration constructor without specifying decoration
Currently you can only create a ControlDecoration by specifying the control and the decoration in the constructor. This works nicely when the decoration is static (ie, always content assist). But there are use cases where the decoration changes depending on the state of the field, and at creation time, it's not clear which decoration will be set. Having a constructor that doesn't require a decoration would be nice.
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ControlDecoration.java
*/
	private boolean showOnlyOnFocus = false;
	/**
	 * Boolean indicating whether the decoration should show its description
	 * text in a hover when the user hovers over the decoration.
	 */
	private boolean showHover = true;
	/**
	 * Margin width used between the decorator and the control.
	 */
	private int marginWidth = 0;
	/**
	 * The focus listener
	 */
	private FocusListener focusListener;
	/**
	 * The dispose listener
	 */
	private DisposeListener disposeListener;
	/**
	 * The paint listener installed for drawing the decoration
	 */
	private PaintListener paintListener;
	/**
	 * The mouse listener installed for tracking the hover
	 */
	private MouseTrackListener mouseListener;
	/**
	 * The mouse move listener installed for tracking the hover
	 */