Bug 144522 [Field Assist] - should proposal popup ever open if empty?
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
* @see org.eclipse.jface.fieldassist.IContentProposalListener
	 */
	public void addContentProposalListener(IContentProposalListener listener) {
		proposalListeners.add(listener);
	}
	/*
	 * Add our listener to the control. Debug information to be left in until
	 * this support is stable on all platforms.
	 */
	private void addControlListener(Control control) {
		if (DEBUG) {
			System.out
					.println("ContentProposalListener#installControlListener()"); 
		}
		if (controlListener != null) {
			return;
		}
		controlListener = new Listener() {
			public void handleEvent(Event e) {
				if (!isEnabled) {
					return;
				}
				switch (e.type) {
				case SWT.Traverse:
				case SWT.KeyDown:
					if (DEBUG) {
						StringBuffer sb;
						if (e.type == SWT.Traverse) {
							sb = new StringBuffer("Traverse"); 
						} else {