Bug 126658 [CommonNavigator] [DND] Complete definition of DND API
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentService.java
NavigatorContentDescriptor[] descriptors = CONTENT_DESCRIPTOR_REGISTRY
				.getAllContentDescriptors();
		for (int i = 0; i < descriptors.length; i++) {
			if (assistant.isVisible(descriptors[i].getId()))
				visibleDescriptors.add(descriptors[i]);
		}
		if (visibleDescriptors.isEmpty())
			return NO_DESCRIPTORS;
		return (INavigatorContentDescriptor[]) visibleDescriptors
				.toArray(new INavigatorContentDescriptor[visibleDescriptors
						.size()]);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.navigator.INavigatorContentService#bindExtensions(java.lang.String[],
	 *      boolean)
	 */
	public INavigatorContentDescriptor[] bindExtensions(String[] extensionIds,
			boolean isRoot) {
		if (extensionIds == null || extensionIds.length == 0)
			return NO_DESCRIPTORS;
		for (int i = 0; i < extensionIds.length; i++)
			assistant.bindExtensions(extensionIds, isRoot);
		Set boundDescriptors = new HashSet();
		INavigatorContentDescriptor descriptor;
		for (int i = 0; i < extensionIds.length; i++) {
			descriptor = CONTENT_DESCRIPTOR_REGISTRY
					.getContentDescriptor(extensionIds[i]);
			if (descriptor != null)