Rolled expect_tests 0.3.15
Rolled expect_tests 0.3.15

BUG=511380

Review URL: https://codereview.chromium.org/1249473002

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