Bug 11748 switch to new DecoratorManager API
From the workbench change notes: API changes IWorkbenchPartSite.getDecoratorManager() - As the DecoratorManager has proven to be required for more than just IWorkbenchPartSites we have moved getDecoratorManager() to IWorkbench and deprecated the getDecoratorManager() in IWorkbenchPartSite. The one in IWorkbenchPartSite will be removed after the other Eclipse components have had a chance to switch to the new API.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
fFilterWorkingSetAction.setChecked(ws != null);
		fRemoveWorkingSetAction.setEnabled(ws != null);
	} 
	
	/**
	 * Returns the shell to use for opening dialogs.
	 * Used in this class, and in the actions.
	 */
	private Shell getShell() {
		return fViewer.getTree().getShell();
	}
	/**
	 * Returns the selection provider.
	 */
	private ISelectionProvider getSelectionProvider() {
		return fViewer;
	}
	
	/**
	 * Returns the current selection.
	 */
	private ISelection getSelection() {
		return fViewer.getSelection();
	}
	  
	
	
	/**
	 * Called when the context menu is about to open. Override
	 * to add your own context dependent menu contributions.