Mark two traversal tess a flaky

TBR=dglazkov@chromium.org
BUG=313219

Review URL: https://codereview.chromium.org/50043008

git-svn-id: svn://svn.chromium.org/blink/trunk@160928 bbb929c8-8fbe-4397-9dbb-9b2b20218538