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
* 
	 * @param acceptance
	 *            a constant indicating how an accepted proposal should affect
	 *            the control's content. Should be one of
	 *            <code>PROPOSAL_INSERT</code>, <code>PROPOSAL_REPLACE</code>,
	 *            or <code>PROPOSAL_IGNORE</code>
	 */
	public void setProposalAcceptanceStyle(int acceptance) {
		proposalAcceptanceStyle = acceptance;
	}
	/**
	 * Return the integer style that indicates how keystrokes affect the content
	 * of the proposal popup while it is open.
	 * 
	 * @return a constant indicating how keystrokes in the proposal popup affect
	 *         filtering of the proposals shown. <code>FILTER_NONE</code>
	 *         specifies that no filtering will occur in the content proposal
	 *         list as keys are typed. <code>FILTER_CUMULATIVE</code>
	 *         specifies that the content of the popup will be filtered by a
	 *         string containing all the characters typed since the popup has
	 *         been open. <code>FILTER_CHARACTER</code> specifies the content
	 *         of the popup will be filtered by the most recently typed
	 *         character. The default is <code>FILTER_NONE</code>.
	 */
	public int getFilterStyle() {
		return filterStyle;
	}
	/**
	 * Set the integer style that indicates how keystrokes affect the content of
	 * the proposal popup while it is open. Popup-based filtering is useful for