Bug 126658 [CommonNavigator] [DND] Complete definition of DND API
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/extensions/NavigatorContentDescriptor.java
.getAttribute(ATT_ACTIVE_BY_DEFAULT);
		activeByDefault = (activeByDefaultString != null && activeByDefaultString
				.length() > 0) ? Boolean.valueOf(
				configElement.getAttribute(ATT_ACTIVE_BY_DEFAULT))
				.booleanValue() : true;
		if (priorityString != null) {
			try {
				Priority p = Priority.get(priorityString);
				priority = p != null ? p.getValue()
						: Priority.NORMAL_PRIORITY_VALUE;
			} catch (NumberFormatException exception) {
				priority = Priority.NORMAL_PRIORITY_VALUE;
			}
		}
		if (id == null) {
			throw new WorkbenchException(NLS.bind(
					CommonNavigatorMessages.Attribute_Missing_Warning,
					new Object[] {
							ATT_ID,
							configElement.getDeclaringExtension()
									.getUniqueIdentifier(),
							configElement.getDeclaringExtension()
									.getNamespace() }));
		}
		IConfigurationElement[] children = configElement
				.getChildren(TAG_ENABLEMENT);
		if (children.length == 0) {
			children = configElement.getChildren(TAG_TRIGGER_POINTS);
			if (children.length == 1) {
				enablement = new CustomAndExpression(children[0]);