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This change removes almost all the remaining overrides of ::Close() in cbuiv,
and some of the overrides of other methods. Replacements are either:

1) Deleted outright
2) Replaced with lambdas inlined in the constructor
3) Replaced with void OnDialog*() methods that are used for the new callback
   system

Bug: 1011446
Change-Id: Idfe315895958f7cc92db17a30fc4cf591e4ffec8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2036943
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#739090}