Bug 265422 [FieldAssist] Field assist hint popup border is black
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ControlDecoration.java
private int listenerInstalls = 0;
	/**
	 * The current rectangle used for tracking mouse moves
	 */
	private Rectangle decorationRectangle;
	
	/**
	 * The rectangle of the previously used image.  Used
	 * for redrawing in the case where a smaller image replaces
	 * a larger one.
	 * 
	 * @since 3.5
	 */
	private Rectangle previousDecorationRectangle;
	/**
	 * An internal flag tracking whether we have focus. We use this rather than
	 * isFocusControl() so that we can set the flag as soon as we get the focus
	 * callback, rather than having to do an asyncExec in the middle of a focus
	 * callback to ensure that isFocusControl() represents the outcome of the
	 * event.
	 */
	private boolean hasFocus = false;
	/**
	 * The hover used for showing description text
	 */
	private Hover hover;
	/**
	 * The hover used to show a decoration image's description.
	 */
	class Hover {