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This CL refactors previous animations for tray background views
to use layer transforms and also adds a new bounce animation
to be used for holding space and screen recorder tray buttons.

Bug: 896739
Change-Id: I29ce064d44eda7ebb3b98f856ba9b2171be0c549
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2589454
Commit-Queue: Ahmed Mehfooz <amehfooz@chromium.org>
Reviewed-by: Toni Baržić <tbarzic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837029}