[Chromedriver] Delete the dummyCookie which is created for validating domain
[Chromedriver] Delete the dummyCookie which is created for validating domain

BUG=chromedriver:824

Review URL: https://codereview.chromium.org/1564203005

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#369216}

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