Bug 126658 [CommonNavigator] [DND] Complete definition of DND API
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/dnd/CommonDropDescriptorManager.java
/**
	 * A map of (INavigatorContentDescriptor,
	 * CommonDropAdapterDescriptor)-pairs.
	 */
	private final Map dropDescriptors = new HashMap();
	/**
	 * 
	 * @return An initialized singleton instance of the
	 *         CommonDropDescriptorManager.
	 */
	public CommonDropDescriptorManager getInstance() {
		return INSTANCE;
	}
	private CommonDropDescriptorManager() {
		new CommonDropAdapterRegistry().readRegistry();
	}
	
	
	/**
	 * @param aContentDescriptor
	 *            A non-null content descriptor. 
	 * @param aDropDescriptor
	 *            A non-null drop descriptor.
	 */
	private void addCommonDropAdapter(
			INavigatorContentDescriptor aContentDescriptor,
			CommonDropAdapterDescriptor aDropDescriptor) {
		dropDescriptors.put(aContentDescriptor, aDropDescriptor);
	}
	private class CommonDropAdapterRegistry extends