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
throws CoreException;
	/**
	 * Returns whether the given resource is accessible, where files and folders
	 * are always considered accessible, and where a project is accessible iff it
	 * is open.
	 *
	 *	@param resource the resource
	 *	@return <code>true</code> if the resource is accessible, and 
	 *     <code>false</code> if it is not
	 */
	boolean isAccessible(IResource resource) {
		switch (resource.getType()) {
			case IResource.FILE :
				return true;
			case IResource.FOLDER :
				return true;
			case IResource.PROJECT :
				return ((IProject) resource).isOpen();
			default :
				return false;
		}
	}
	/**
	 * Returns whether the given resource is a descendent of any of the resources
	 * in the given list.
	 *
	 * @param resources the list of resources (element type: <code>IResource</code>)
	 * @param child the resource to check
	 * @return <code>true</code> if <code>child</code> is a descendent of any of the
	 *   elements of <code>resources</code>