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This patch adds an animation to show next image.

Bug: b/137228115
Test: new PhotoModelTest.* and manual

Change-Id: I70e2067cb35b5315c201c0d3769c5c092005fd5a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1762061Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Tao Wu <wutao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694339}