Bug 127080 [Field Assist] widget disposed error on proposal insertion
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
* The list of listeners who wish to be notified when something significant
	 * happens with the proposals.
	 */
	private ListenerList proposalListeners = new ListenerList();
	/*
	 * Flag that indicates whether the adapter is enabled. In some cases,
	 * adapters may be installed but depend upon outside state.
	 */
	private boolean isEnabled = true;
	/*
	 * The delay in milliseconds used when autoactivating the popup.
	 */
	private int autoActivationDelay = 0;
	/*
	 * The desired size in pixels of the proposal popup.
	 */
	private Point popupSize;
	/**
	 * Construct a content proposal adapter that can assist the user with
	 * choosing content for the field.
	 * 
	 * @param control
	 *            the control for which the adapter is providing content assist.
	 *            May not be <code>null</code>.
	 * @param controlContentAdapter
	 *            the <code>IControlContentAdapter</code> used to obtain and
	 *            update the control's contents as proposals are accepted. May
	 *            not be <code>null</code>.
	 * @param proposalProvider
	 *            the <code>IContentProposalProvider</code> used to obtain