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
return showHover;
	}
	/**
	 * Set the boolean that controls whether the decoration's description text
	 * should be shown in a hover when the user hovers over the decoration. The
	 * default value of this setting is <code>true</code>.
	 * 
	 * @param showHover
	 *            <code>true</code> if a hover popup containing the
	 *            decoration's description text should be shown when the user
	 *            hovers over the decoration, and <code>false</code> if a
	 *            hover should not be shown.
	 */
	public void setShowHover(boolean showHover) {
		this.showHover = showHover;
		update();
	}
	/**
	 * Get the margin width in pixels that should be used between the decorator
	 * and the horizontal edge of the control. The default value of this setting
	 * is <code>0</code>.
	 * 
	 * @return the number of pixels that should be reserved between the
	 *         horizontal edge of the control and the adjacent edge of the
	 *         decoration.
	 */
	public int getMarginWidth() {
		return marginWidth;
	}
	/**