Deflake fast/css/no-recalc-on-no-op-inline-style-changes.html

The test had an assumption about a style recalc count at a point during
loading which was not preceeded by a forced recalc at any point. The
result was undefined and it did not test anything useful. Add a forced
recalc through offsetTop before the test instead.

Bug: 904587
Change-Id: I17d00e017a625ca10f71ebfd3a946266d6ea9ff5
Reviewed-on: https://chromium-review.googlesource.com/c/1332431
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607536}
2 files changed