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In http://crrev.com/c/1354559, the thread waiting for the blocking
Windows WebAuthn API calls to return was moved into the WinWebAuthnApi
singleton. Unfortunately, this introduced a potential use-after-free, because
arguments to the blocking API calls get passed via pointer and the owner of those
arguments, WinHelloApiAuthenticator, wasn't generally guaranteed to outlive the
duration of the request.

This change fixes the issue by moving all data passed to the Windows API calls
into WinWebAuthnApi by value.

Bug: 898718
Change-Id: Ib4f2e86f4ef04cbac712682d4cff386709e735eb
Reviewed-on: https://chromium-review.googlesource.com/c/1356334
Commit-Queue: Martin Kreichgauer <martinkr@chromium.org>
Reviewed-by: Adam Langley <agl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612753}