Bug 144522 [Field Assist] - should proposal popup ever open if empty?
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
* Strings from non-String proposals.
	 */
	private ILabelProvider labelProvider;
	/*
	 * The control for which content proposals are provided.
	 */
	private Control control;
	/*
	 * The adapter used to extract the String contents from an arbitrary
	 * control.
	 */
	private IControlContentAdapter controlContentAdapter;
	/*
	 * The popup used to show proposals.
	 */
	private ContentProposalPopup popup;
	/*
	 * The keystroke that signifies content proposals should be shown.
	 */
	private KeyStroke triggerKeyStroke;
	/*
	 * The String containing characters that auto-activate the popup.
	 */
	private String autoActivateString;
	/*
	 * Integer that indicates how an accepted proposal should affect the
	 * control. One of PROPOSAL_IGNORE, PROPOSAL_INSERT, or PROPOSAL_REPLACE.
	 * Default value is PROPOSAL_INSERT.
	 */
	private int proposalAcceptanceStyle = PROPOSAL_INSERT;