Bug 204843 [Field Assist] - API - should deprecate FILTER_CUMULATIVE in ContentProposalAdapter
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
proposalListeners2.add(listener);
	}
	/**
	 * Remove the specified listener from the list of content proposal listeners
	 * that are notified when a content proposal popup is opened or closed.
	 * </p>
	 * 
	 * @param listener
	 *            the IContentProposalListener2 to be removed as a listener.
	 *            Must not be <code>null</code>. If the listener has not
	 *            already been registered, this method has no effect.
	 * 
	 * @since 3.3
	 * @see org.eclipse.jface.fieldassist.IContentProposalListener2
	 */
	public void removeContentProposalListener(IContentProposalListener2 listener) {
		proposalListeners2.remove(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;
		}