Bug 315281 update copyrights for 3.6
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/dnd/CommonDropDescriptorManager.java
private static final CommonDropDescriptorManager INSTANCE = new CommonDropDescriptorManager();
	private static final CommonDropAdapterDescriptor[] NO_DESCRIPTORS = new CommonDropAdapterDescriptor[0];
	/**
	 * A map of (INavigatorContentDescriptor,
	 * CommonDropAdapterDescriptor)-pairs.
	 */
	private final Map dropDescriptors = new TreeMap(ExtensionSequenceNumberComparator.INSTANCE);
	/**
	 * 
	 * @return An initialized singleton instance of the
	 *         CommonDropDescriptorManager.
	 */
	public static CommonDropDescriptorManager getInstance() {
		return INSTANCE;
	}
	private CommonDropDescriptorManager() {
		new CommonDropAdapterRegistry().readRegistry();
	}
	/**
	 * 
	 * @param aDropTarget