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This change makes cancel/close available on the UI, available as a
direct action with the same behavior when the UI is up.

When the UI is not up, "cancel" is only available if it exists in
UserAction as a direct action. When the UI is up, "cancel" is executed
through the UIController instead of being run directly as a UserAction.

This allows closing the UI or showing the undoable snackbar as a result
of the "cancel" direct action being executed.

Bug: b/134742442
Change-Id: Ia43275a090a0ad2a440447b175fdcf15dd893430
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1699675
Commit-Queue: Stephane Zermatten <szermatt@chromium.org>
Reviewed-by: Jordan Demeulenaere <jdemeulenaere@chromium.org>
Cr-Commit-Position: refs/heads/master@{#680429}