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This CL adds the recording logic for AccountPasswordsConsent to the
SigninReauthUI. This requires:
* Collecting the relevant strings in JS and sending them back to C++.
* Maintaining a mapping between strings and GRD IDs in C++, to convert
  the strings from JS back into IDs.
* Putting the IDs into a AccountPasswordsConsent proto and sending that
  to the ConsentAuditor.

Bug: 1111252
Change-Id: Ic06533fdb361b415398923b12fbc3c289a47e989
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2352789
Commit-Queue: Marc Treib <treib@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Reviewed-by: Alex Ilin <alexilin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797726}