[LayoutNG] Comma instead of 'x' as separator between coordinates in ToString().

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: I96dcb6728816c030fffda7fa67a0a90eb7d1fe5f
Reviewed-on: https://chromium-review.googlesource.com/650255
Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#499654}
2 files changed