Bug 176764 [Undo] - DeleteResourcesOperation does not handle overlapped selections
In a project, create a folder f1. In f1, create another folder f2. Select f1 and f2 delete The undo fails with a "not enough info to restore" message. The problem is that the resource description for f2 checks to see whether f2's parent is valid, and at the time of the check, f1 has not been restored. Either the validity check needs to be smarter, or else the deletes should be collapsed into just f1.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/undo/AbstractResourcesOperation.java
*/
	protected void setResourceDescriptions(ResourceDescription[] descriptions) {
		if (descriptions == null) {
			resourceDescriptions = new ResourceDescription[0];
		} else {
			resourceDescriptions = descriptions;
		}
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.ide.undo.AbstractWorkspaceOperation#appendDescriptiveText(java.lang.StringBuffer)
	 */
	protected void appendDescriptiveText(StringBuffer text) {
		super.appendDescriptiveText(text);
		text.append(" resourceDescriptions: "); 
		text.append(resourceDescriptions);
		text.append('\'');
	}
	/**
	 * Compute a scheduling rule for creating resources.
	 * 
	 * @return a scheduling rule appropriate for creating the resources
	 *         specified in the resource descriptions
	 */
	protected ISchedulingRule computeCreateSchedulingRule() {
		ISchedulingRule[] ruleArray = new ISchedulingRule[resourceDescriptions.length * 3];
		for (int i = 0; i < resourceDescriptions.length; i++) {
			IResource resource = resourceDescriptions[i].createResourceHandle();