Bug 164529 [FieldAssist] Provide the ability to listen to start and end field assist events
In the previous content assist functionality, an ICompletionListener could be specified to listen to the following events: public void assistSessionEnded(ContentAssistEvent event) public void assistSessionStarted(ContentAssistEvent event) The equivalent listener, IContentProposalListener, does not listen to those two events. PDE needs to know when an assist session is ended in order to reset the state it maintains for custom filtering of java type results. The current event does not handle the case where the user ends the content assist without selecting a proposal: public void proposalAccepted(IContentProposal proposal);
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
* open.
	 * 
	 * @param propagateKeys
	 *            a boolean that indicates whether key events (including
	 *            auto-activation characters) should be propagated to the
	 *            adapted control when the proposal popup is open.
	 */
	public void setPropagateKeys(boolean propagateKeys) {
		this.propagateKeys = propagateKeys;
	}
	/**
	 * Return the content adapter that can get or retrieve the text contents
	 * from the adapter's control. This method is used when a client, such as a
	 * content proposal listener, needs to update the control's contents
	 * manually.
	 * 
	 * @return the {@link IControlContentAdapter} which can update the control
	 *         text.
	 */
	public IControlContentAdapter getControlContentAdapter() {
		return controlContentAdapter;
	}
	/**
	 * Set the boolean flag that determines whether the adapter is enabled.
	 * 
	 * @param enabled
	 *            <code>true</code> if the adapter is enabled and responding
	 *            to user input, <code>false</code> if it is ignoring user
	 *            input.
	 *