device/fido/mac: set the User Present (UP) bit in authenticator data

See https://www.w3.org/TR/webauthn/#sec-authenticator-data. AFAIU, the
spec is not exactly clear whether or not to set this bit from a user
verifying authenticator. It says that the bit should be set if the
user is "present", which is defined as having successfully completed a
"user presence test". User presence test is defined separately from user
verification test (which is what Touch ID does). Logically, a user
verification test always includes a user presence test, but the spec
doesn't say so explicitly.

Regardless of what the spec says, setting both bits seems less likely to
confuse server implementations IMO. A naive server e.g. might *just*
check for the UP bit, and if it is not set reject the response, even
though the UV bit is set. Hence, we should probably set both.

Bug: 678128
Change-Id: I02be366dba324e4f9b83ba0d354a674242fc72dc
Reviewed-on: https://chromium-review.googlesource.com/1137216
Commit-Queue: Martin Kreichgauer <martinkr@google.com>
Reviewed-by: Kim Paulhamus <kpaulhamus@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575386}

device/fido/mac/util.mm

@@ -103,6 +103,7 @@ base::Optional<AuthenticatorData> MakeAuthenticatorData(
   std::array<uint8_t, 2> encoded_credential_id_length = {
       0, static_cast<uint8_t>(credential_id.size())};
   constexpr uint8_t flags =
+      static_cast<uint8_t>(AuthenticatorData::Flag::kTestOfUserPresence) |
       static_cast<uint8_t>(AuthenticatorData::Flag::kTestOfUserVerification) |
       static_cast<uint8_t>(AuthenticatorData::Flag::kAttestation);
   return AuthenticatorData(