Mark 2 more tests as flaky found from try-runs

BUG=374282, 374284
TBR=japhet

Review URL: https://codereview.chromium.org/286973010

git-svn-id: svn://svn.chromium.org/blink/trunk@174192 bbb929c8-8fbe-4397-9dbb-9b2b20218538