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Also modified MultiStepBehavior in a way that it hides current step
before hide the whole screen. And shows the current step back when
screen is show again.

Bug: 1155468
Change-Id: Iae4d920774360c5379b0adb5c32a70747c728cfd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2571100
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Reviewed-by: Denis Kuznetsov [CET] <antrim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834682}