Bug 132039 [Field Assist] - secondary popup should update on same delay as its invocation delay
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
* @param listener
	 *            the IContentProposalListener to be added as a listener. Must
	 *            not be <code>null</code>. If an attempt is made to register
	 *            an instance which is already registered with this instance,
	 *            this method has no effect.
	 * 
	 * @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: