Bug 65276 [Preferences] Preference dialog should disable OK when okPressed
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/PreferenceDialog.java
/**
	 * Sets whether a Help button is available for this dialog.
	 * <p>
	 * Clients must call this framework method before the dialog's control has
	 * been created.
	 * <p>
	 * 
	 * @param b
	 *            <code>true</code> to include a Help button, and
	 *            <code>false</code> to not include one (the default)
	 */
	public void setHelpAvailable(boolean b) {
		isHelpAvailable = b;
	}
	/**
	 * Set the message text. If the message line currently displays an error,
	 * the message is stored and will be shown after a call to clearErrorMessage
	 * <p>
	 * Shortcut for <code>setMessage(newMessage, NONE)</code>
	 * </p>
	 * 
	 * @param newMessage
	 *            the message, or <code>null</code> to clear the message
	 */
	public void setMessage(String newMessage) {
		setMessage(newMessage, IMessageProvider.NONE);
	}
	/**
	 * Sets the message for this dialog with an indication of what type of
	 * message it is.