ChromeOS cryptohome should be able to use gaia id as user identifier.

chromeos/attestation/mock_attestation_flow.h

Index: chromeos/attestation/mock_attestation_flow.h
diff --git a/chromeos/attestation/mock_attestation_flow.h b/chromeos/attestation/mock_attestation_flow.h
index fad04f0d62adf3126e2e4b8db53798afea552d39..d64548ed8080354c6552ca37fde38f777c45f12b 100644
--- a/chromeos/attestation/mock_attestation_flow.h
+++ b/chromeos/attestation/mock_attestation_flow.h
@@ -11,6 +11,8 @@
 #include "base/macros.h"
 #include "testing/gmock/include/gmock/gmock.h"
 
+class AccountId;
+
 namespace chromeos {
 namespace attestation {
 
@@ -66,11 +68,12 @@ class MockAttestationFlow : public AttestationFlow {
   MockAttestationFlow();
   virtual ~MockAttestationFlow();
 
-  MOCK_METHOD5(GetCertificate, void(AttestationCertificateProfile,
-                                    const std::string&,
-                                    const std::string&,
-                                    bool,
-                                    const CertificateCallback&));
+  MOCK_METHOD5(GetCertificate,
+               void(AttestationCertificateProfile,
+                    const AccountId& account_id,
+                    const std::string&,
+                    bool,
+                    const CertificateCallback&));
 };
 
 }  // namespace attestation