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
}
	/**
	 * Handles double clicks in viewer.
	 * Opens editor if file double-clicked.
	 */
	private void handleDoubleClick(DoubleClickEvent event) {
		IStructuredSelection s= (IStructuredSelection) event.getSelection();
		Object element= s.getFirstElement();
		
		if (fOpenCUAction.isEnabled()) {
			fOpenCUAction.run();
			return;
		}
		
		if (fViewer.isExpandable(element)) {
			if (JavaBasePreferencePage.doubleClickGoesInto()) {
				
				if (element instanceof IOpenable && 
					!(element instanceof ICompilationUnit) && 
					!(element instanceof IClassFile)) {
					fZoomInAction.run();
				}
			} else {
				fViewer.setExpandedState(element, !fViewer.getExpandedState(element));
				
			}
		}
	}
	/**
	 * Handles selection changed in viewer.