Use assertAlmostEqual in interface_test to fix flakes
Use assertAlmostEqual in interface_test to fix flakes

BUG=511334

Review URL: https://codereview.chromium.org/1251703002

nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra