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This adds interactive UI tests for all ways of terminating a
snoozeable promo:
* User clicking the snooze button
* User clicking the dismiss button
* Closing the promo through FeaturePromoController
* Directly closing the promo's widget (as if the user pressed ESC)

The tests verify the snooze profile prefs are set correctly after
these operations.

Bug: 1121399
Change-Id: I5ab462d51abc771edc0d27afb5093d756e7e3ccd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2441115
Auto-Submit: Collin Baker <collinbaker@chromium.org>
Commit-Queue: Wei Li <weili@chromium.org>
Reviewed-by: Wei Li <weili@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812774}