Improve TpmAttestationGetPublicKey function in FakeCryptohomeClient

This change fixes a bug that prevented FakeCryptohomeClient from
answering on TpmAttestationGetPublicKey request and adds a helper
function to configure its result.

Bug: 1045895
Change-Id: I4f7a72c2768f78df97c43756932ca7700a62b999
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2050277Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Commit-Queue: Michael Ershov <miersh@google.com>
Cr-Commit-Position: refs/heads/master@{#740599}

chromeos/dbus/cryptohome/fake_cryptohome_client.cc

@@ -60,6 +60,9 @@ FakeCryptohomeClient::FakeCryptohomeClient() {
             base::PathExists(cache_path);
   if (locked_)
     LoadInstallAttributes();
+
+  set_tpm_attestation_public_key(
+      TpmAttestationDataResult{true, "fake_public_key_for_test"});
 }
 
 FakeCryptohomeClient::~FakeCryptohomeClient() {
@@ -453,7 +456,7 @@ void FakeCryptohomeClient::TpmAttestationGetPublicKey(
     DBusMethodCallback<TpmAttestationDataResult> callback) {
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE,
-      base::BindOnce(std::move(callback), TpmAttestationDataResult{}));
+      base::BindOnce(std::move(callback), tpm_attestation_public_key_));
 }
 
 void FakeCryptohomeClient::TpmAttestationRegisterKey(
@@ -461,7 +464,7 @@ void FakeCryptohomeClient::TpmAttestationRegisterKey(
     const cryptohome::AccountIdentifier& cryptohome_id,
     const std::string& key_name,
     AsyncMethodCallback callback) {
-  ReturnAsyncMethodData(std::move(callback), std::string());
+  ReturnAsyncMethodResult(std::move(callback));
 }
 
 void FakeCryptohomeClient::TpmAttestationSignEnterpriseChallenge(

chromeos/dbus/cryptohome/fake_cryptohome_client.h

@@ -321,6 +321,11 @@ class COMPONENT_EXPORT(CRYPTOHOME_CLIENT) FakeCryptohomeClient
     tpm_attestation_does_key_exist_should_succeed_ = should_succeed;
   }
 
+  void set_tpm_attestation_public_key(
+      base::Optional<TpmAttestationDataResult> value) {
+    tpm_attestation_public_key_ = value;
+  }
+
   void set_supports_low_entropy_credentials(bool supports) {
     supports_low_entropy_credentials_ = supports;
   }
@@ -486,6 +491,7 @@ class COMPONENT_EXPORT(CRYPTOHOME_CLIENT) FakeCryptohomeClient
   bool enable_auth_check_ = false;
   bool tpm_is_ready_ = true;
   bool tpm_is_enabled_ = true;
+  base::Optional<TpmAttestationDataResult> tpm_attestation_public_key_;
 
   // Reply to GetRsuDeviceId().
   std::string rsu_device_id_;