Bug 270008 [CommonNavigator] Ability to extend bindings beyond "inheritsBindingsFrom" tag
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/extensions/NavigatorViewerDescriptorManager.java
String viewerId = element.getAttribute(ATT_VIEWER_ID);
				NavigatorViewerDescriptor descriptor = getNavigatorViewerDescriptor(viewerId);
				descriptor.consumeContentBinding(element);
				return true;
			}
			if (TAG_VIEWER_ACTION_BINDING.equals(element.getName())) {
				String viewerId = element.getAttribute(ATT_VIEWER_ID);
				NavigatorViewerDescriptor descriptor = getNavigatorViewerDescriptor(viewerId);
				descriptor.consumeActionBinding(element);
				return true;
			} if (TAG_DRAG_ASSISTANT.equals(element.getName())) {
				String viewerId = element.getAttribute(ATT_VIEWER_ID);
				NavigatorViewerDescriptor descriptor = getNavigatorViewerDescriptor(viewerId);
				descriptor.addDragAssistant(new CommonDragAssistantDescriptor(element));
				return true;
			}
			return false;
		}
		
		public void readRegistry() {
			IExtensionRegistry registry = Platform.getExtensionRegistry();
			IExtensionPoint point = registry.getExtensionPoint(NavigatorPlugin.PLUGIN_ID, TAG_VIEWER);
			if (point == null) {
				return;
			}
			super.readRegistry();
		}
	}
}