Bug 125955 [Field Assist] - StringIndexOutOfBoundsException when backspacing out of a filter
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
* Flag that indicates whether the adapter is enabled. In some cases,
	 * adapters may be installed but depend upon outside state.
	 */
	private boolean isEnabled = true;
	/*
	 * The delay in milliseconds used when autoactivating the popup.
	 */
	private int autoActivationDelay = 0;
	/**
	 * Construct a content proposal adapter that can assist the user with
	 * choosing content for the field.
	 * 
	 * @param control
	 *            the control for which the adapter is providing content assist.
	 *            May not be <code>null</code>.
	 * @param controlContentAdapter
	 *            the <code>IControlContentAdapter</code> used to obtain and
	 *            update the control's contents as proposals are accepted. May
	 *            not be <code>null</code>.
	 * @param proposalProvider
	 *            the <code>IContentProposalProvider</code> used to obtain
	 *            content proposals for this control, or <code>null</code> if
	 *            no content proposal is available.
	 * @param labelProvider
	 *            the label provider which provides text and image information
	 *            for content proposals. A <code>null</code> value indicates
	 *            that no label provider is needed, and all values will be
	 *            obtained from the proposals themselves. The lifecycle of the
	 *            specified label provider is not managed by this adapter.
	 *            Clients must dispose the label provider when it is no longer