Fix LayoutUnit float test

The test expectations were confusingly off-by-one, marked
under a bug that doesn't apply to the test (crbug.com/360889).

R=eae@chromium.org, pdr@chromium.org

Review URL: https://codereview.chromium.org/681123002

git-svn-id: svn://svn.chromium.org/blink/trunk@184489 bbb929c8-8fbe-4397-9dbb-9b2b20218538