Bug 126658 [CommonNavigator] [DND] Complete definition of DND API
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentService.java
NavigatorContentDescriptor descriptor = (NavigatorContentDescriptor) descriptorList
						.get(i);
				activatedExtensions[i] = descriptor.getId();
				activatedDescriptors.add(descriptor);
			}
			NavigatorActivationService.getInstance()
					.activateNavigatorExtension(viewerId, activatedExtensions,
							true);
		}
		if (activatedDescriptors.size() == 0)
			return NO_DESCRIPTORS;
		return (INavigatorContentDescriptor[]) activatedDescriptors
				.toArray(new NavigatorContentDescriptor[activatedDescriptors
						.size()]);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.internal.navigator.INavigatorContentService#createCommonContentProvider()
	 */
	public ITreeContentProvider createCommonContentProvider() {
		if (contentProviderInitialized)
			return contentProvider;
		synchronized (this) {
			if (contentProvider == null)
				contentProvider = new NavigatorContentServiceContentProvider(
						this);
			contentProviderInitialized = true;
		}
		return contentProvider;