Fix typo in preserve-3d test

With this patch, the following test no longer fails due to a typo:
preserve-3d-flat-grouping-properties-containing-block.tentative.html

Bug: 1008483
Change-Id: Iaf1ad7f5ca3e94d20355ecfe737d5d346fca2a05
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2798531
Commit-Queue: Philip Rogers <pdr@chromium.org>
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Auto-Submit: Philip Rogers <pdr@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#868277}
diff --git a/css/css-transforms/preserve-3d-flat-grouping-properties-containing-block.tentative.html b/css/css-transforms/preserve-3d-flat-grouping-properties-containing-block.tentative.html
index e30607c..2c451f3 100644
--- a/css/css-transforms/preserve-3d-flat-grouping-properties-containing-block.tentative.html
+++ b/css/css-transforms/preserve-3d-flat-grouping-properties-containing-block.tentative.html
@@ -31,8 +31,6 @@
 </div>
 
 <script>
-  nonflatWidth = nonflat.getBoundingClientRect().width;
-
   test(function() {
     assert_equals(absoluteUnderGrouping.offsetParent, parentWithGrouping);
   }, "Preserve-3d element with a grouping property still a containing block");