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1. Move the baseline of the title at the center of the screen;
2. Increase the margin around bottom button group, and made adjust to
small screen devices;
3. Center the ToS and UMA components between the title and accept button

Bug: 1120842
Change-Id: Ie6ab2f4322d1ffd2e2614987424c636604797c61
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391268Reviewed-by: Sky Malice <skym@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Commit-Queue: Wenyu Fu <wenyufu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805459}