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These tests were likely flaky because of a race between setPermission and
the subsequent request.

Utilize the new helper function for setting permissions to rewrite the
tests in terms of promises and remove the races.

BUG=519007

Review URL: https://codereview.chromium.org/1309873002

git-svn-id: svn://svn.chromium.org/blink/trunk@201063 bbb929c8-8fbe-4397-9dbb-9b2b20218538