Bug 53582 Rebuild Project are not run in the background?
The "Build All" and "Rebuild All" actions are run in the background, but the "Build Project" and "Rebuild Project" actions aren't. This is not consistent and I was surprised to get a modal dialog when performing a "Rebuild Project".
bundles/org.eclipse.ui.ide/extensions/org/eclipse/ui/actions/WorkspaceAction.java
*/
	boolean isDescendent(List resources, IResource child) {
		IResource parent = child.getParent();
		return parent != null && (resources.contains(parent) || isDescendent(resources, parent));
	}
	/**
	 * Performs pruning on the given list of resources, as described in 
	 * <code>shouldPerformResourcePruning</code>.
	 *
	 * @param resourceCollection the list of resources (element type: 
	 *    <code>IResource</code>)
	 * @return the list of resources (element type: <code>IResource</code>)
	 *		after pruning. 
	 * @see #shouldPerformResourcePruning
	 */
	List pruneResources(List resourceCollection) {
		List prunedList = new ArrayList(resourceCollection);
		Iterator elementsEnum = prunedList.iterator();
		while (elementsEnum.hasNext()) {
			IResource currentResource = (IResource) elementsEnum.next();
			if (isDescendent(prunedList, currentResource))
				elementsEnum.remove(); 
		}
		return prunedList;
	}
	/**
	 * Records the core exception to be displayed to the user
	 * once the action is finished.
	 *
	 * @param error a <code>CoreException</code>