Bug 189490 [CommonNavigator] Go To->Resource won't enable
I0524 1. Open the Project Explorer in the Resource perspective 2. Create a vanilla project P 3. Create a folder F 4. Create a file resource R Open the Navigate->Go To file. "Resource..." will remain disabled.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentService.java
* @return The set of {@link INavigatorContentExtension}s that are
	 *         <i>visible</i> and <i>active</i> for this content service and
	 *         have a <b>possibleChildren</b> expression that is <i>enabled</i>
	 *         for the given element.
	 */
	public Set findContentExtensionsWithPossibleChild(Object anElement,
			boolean toLoadIfNecessary) {
		Set enabledDescriptors = findDescriptorsWithPossibleChild(anElement);
		return extractDescriptorInstances(enabledDescriptors, toLoadIfNecessary);
	}
	/**
	 * Remember that the elements in the given array came from the given source
	 * 
	 * @param source
	 *            The descriptor of the extension that contributed the set of
	 *            elements.
	 * @param elements
	 *            An array of elements from the given source.
	 */
	public synchronized void rememberContribution(
			NavigatorContentDescriptor source, Object[] elements) {
		if (source != null && elements != null) {
			for (int i = 0; i < elements.length; i++)
				rememberContribution(source, elements[i]);
		}
	}
	/**
	 * Remember that the elements in the given array came from the given source
	 * 
	 * @param source