Wait for the attestation to be ready (TPM being prepared for attestation) before trying to enroll.

chromeos/attestation/attestation_flow.h

Index: chromeos/attestation/attestation_flow.h
diff --git a/chromeos/attestation/attestation_flow.h b/chromeos/attestation/attestation_flow.h
index 26a7292d60a9d4eab6901f21e268e31b6a799846..ef344e802e5cf720412a223b9d8aab0f47c7be73 100644
--- a/chromeos/attestation/attestation_flow.h
+++ b/chromeos/attestation/attestation_flow.h
@@ -14,10 +14,17 @@
 #include "chromeos/attestation/attestation_constants.h"
 #include "chromeos/chromeos_export.h"
 #include "chromeos/dbus/dbus_method_call_status.h"
+#include "net/base/backoff_entry.h"
 #include "third_party/cros_system_api/dbus/service_constants.h"
 
 class AccountId;
 
+namespace base {
+
+class OneShotTimer;
+
+}  // namespace base
+
 namespace cryptohome {
 
 class AsyncMethodCaller;
@@ -108,8 +115,29 @@ class CHROMEOS_EXPORT AttestationFlow {
                               bool force_new_key,
                               const CertificateCallback& callback);
 
+  // Sets the retry timer for tests.
+  void SetRetryTimerForTest(std::unique_ptr<base::OneShotTimer> retry_timer);
+
  private:
   // Asynchronously initiates the attestation enrollment flow.
+  // If attestation is not ready yet, retry as needed.
+  //
+  // Parameters
+  //   on_failure - Called if any failure occurs.
+  //   next_task - Called on successful enrollment.
+  void InitiateEnroll(const base::Closure& on_failure,
+                      const base::Closure& next_task);
+
+  // Called when atestation is not prepared yet, to re-initiate enrollment
+  // after a delay.
+  //
+  // Parameters
+  //   on_failure - Called if any failure occurs.
+  //   next_task - Called on successful enrollment.
+  void RetryInitiateEnroll(const base::Closure& on_failure,
+                           const base::Closure& next_task);
+
+  // Called when attestation is prepared, to start the actual enrollment flow.
   //
   // Parameters
   //   on_failure - Called if any failure occurs.
@@ -227,6 +255,10 @@ class CHROMEOS_EXPORT AttestationFlow {
   CryptohomeClient* cryptohome_client_;
   std::unique_ptr<ServerProxy> server_proxy_;
 
+  int16_t initiate_enroll_retries_ = 7;  // -1 is unlimited retries.

[apronin1, 2016/12/02 01:36:24]

don't we want unlimited retries by default? why 7 is a good magic number here?
also, it may make sense to let the caller pass this value to constructor

+  std::unique_ptr<base::OneShotTimer> retry_timer_;
+  net::BackoffEntry retry_backoff_;
+
   base::WeakPtrFactory<AttestationFlow> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AttestationFlow);