Cryptohome: Notify about error in async calls if cryptohome is not ready yet.

chromeos/dbus/cryptohome_client.h

Index: chromeos/dbus/cryptohome_client.h
diff --git a/chromeos/dbus/cryptohome_client.h b/chromeos/dbus/cryptohome_client.h
index 816c106b25cef1f53491a8edcef736827a2374ce..8f9a5dc433f05b945b1b6e265755924fb763c9aa 100644
--- a/chromeos/dbus/cryptohome_client.h
+++ b/chromeos/dbus/cryptohome_client.h
@@ -39,6 +39,10 @@ namespace chromeos {
 // initializes the DBusThreadManager instance.
 class CHROMEOS_EXPORT CryptohomeClient : public DBusClient {
  public:
+  // Constant that will be passed to AsyncMethodCallback to indicate that
+  // cryptohome is not ready yet.
+  static const int kNotReadyAsyncId;
+
   // A callback to handle AsyncCallStatus signals.
   typedef base::Callback<void(int async_id,
                               bool return_status,