To prevent MediaStreamPermissionTest* flakiness:
(1) Instead of relying on the old infobar notification system, switch to
    the new infobar responder. (As per crbug.com/354380, observers are now
    preferred to notifications.)
(2) Instead of relying on mock permission bubbles, switch to the new
    PermissionBubbleManager responder.
(3) Remove the polling and timeouts.

To satisfy the requirements of the media test cases, I also updated the
InfoBarResponder. It now can handle infobar replacement and dismissing an
infobar without making a choice.

BUG=295723
R=tommi@chromium.org

Committed: https://crrev.com/ccc25707b9788597c55fb4eaa90109500e1f92cb
Cr-Commit-Position: refs/heads/master@{#333360}

Review URL: https://codereview.chromium.org/1161153003

Cr-Commit-Position: refs/heads/master@{#333685}