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- Add switch to enable/disable helpful/unhelpful buttons.
- Complete the logic to build helpful/unhelpful buttons if switch is on.
- TODO: Replace the button text from GRD.

Bug: 988117
Change-Id: Ia46ca3781fb036de4143193031d5906333158cf4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1730254
Commit-Queue: Hesen Zhang <hesen@chromium.org>
Reviewed-by: Xing Liu <xingliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683770}