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
* popup.
	 */
	public static final int FILTER_CHARACTER = 2;
	/**
	 * Indicates that a cumulative filter applies as keys are typed in the
	 * popup. That is, each character typed will be added to the filter.
	 */
	public static final int FILTER_CUMULATIVE = 3;
	/*
	 * Set to <code>true</code> to use a Table with SWT.VIRTUAL. This is a
	 * workaround for https://bugs.eclipse.org/bugs/show_bug.cgi?id=98585#c40
	 * The corresponding SWT bug is
	 * https://bugs.eclipse.org/bugs/show_bug.cgi?id=90321
	 */
	private static final boolean USE_VIRTUAL = !"motif".equals(SWT.getPlatform()); 
	/*
	 * The delay before showing a secondary popup.
	 */
	private static final int POPUP_DELAY = 750;
	/*
	 * The character height hint for the popup. May be overridden by using
	 * setInitialPopupSize.
	 */
	private static final int POPUP_CHAR_HEIGHT = 10;
	/*
	 * The minimum pixel width for the popup. May be overridden by using
	 * setInitialPopupSize.
	 */
	private static final int POPUP_MINIMUM_WIDTH = 300;
	/*