[layoutng] Improve NGExclusionSpace::operator==

If neither space has exclusions, the two spaces are equal.

exclusions_ is a scoped_refptr, so operator== only compares pointer values.

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: Iea67f268f9a537a27f267441f2afda860d641950
Reviewed-on: https://chromium-review.googlesource.com/1188847
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585994}

third_party/blink/renderer/core/layout/ng/exclusions/ng_exclusion_space.cc

@@ -585,6 +585,8 @@ const NGExclusionSpace::DerivedGeometry& NGExclusionSpace::GetDerivedGeometry()
 }
 
 bool NGExclusionSpace::operator==(const NGExclusionSpace& other) const {
+  if (num_exclusions_ == 0 && other.num_exclusions_ == 0)
+    return true;
   return num_exclusions_ == other.num_exclusions_ &&
          exclusions_ == other.exclusions_;
 }