Check-webkit-style complains if I don't have a bug about this, so here it is. The Chromium LayoutTestController should implement setDefersLoading and goBack in order to enable loader/navigation-while-deferring-loads.html.
This is only applicable if the changes in https://bugs.webkit.org/show_bug.cgi?id=60412 land.
Test related bugs being marked WontFix. TestExpectations will contain bug if still relevant.