Bootstrapping: Send meaningful error code/message from Slave to Master

components/pairing/bluetooth_host_pairing_controller.h

Index: components/pairing/bluetooth_host_pairing_controller.h
diff --git a/components/pairing/bluetooth_host_pairing_controller.h b/components/pairing/bluetooth_host_pairing_controller.h
index a9a9d4010a2a2475e8ce726f217ef7b50546d0ec..8eabce07d5f4cfcc8d706a3eecf29934983b8aec 100644
--- a/components/pairing/bluetooth_host_pairing_controller.h
+++ b/components/pairing/bluetooth_host_pairing_controller.h
@@ -74,6 +74,7 @@ class BluetoothHostPairingController
 
   void ChangeStage(Stage new_stage);
   void SendHostStatus();
+  void SendErrorCodeAndMessage();
 
   void OnGetAdapter(scoped_refptr<device::BluetoothAdapter> adapter);
   void SetPowered();
@@ -109,6 +110,8 @@ class BluetoothHostPairingController
   void OnUpdateStatusChanged(UpdateStatus update_status) override;
   void OnEnrollmentStatusChanged(EnrollmentStatus enrollment_status) override;
   void SetPermanentId(const std::string& permanent_id) override;
+  void SetErrorCodeAndMessage(int error_code,
+                              const std::string& error_message) override;
   void Reset() override;
 
   // ProtoDecoder::Observer:
@@ -148,6 +151,17 @@ class BluetoothHostPairingController
   std::string controller_device_address_;
   bool was_powered_ = false;
 
+  // The format of the |error_code_| is:
+  // [0, "no error"]
+  // [1*, "network error"]
+  // [2*, "authentication error"], e.g., [21, "Service unavailable"], ...
+  // [3*, "enrollment error"], e.g., [31, "DMserver registration error"], ...
+  // [4*, "other error"]
+  // The |error_code_| and |error_message_| will pass over to the master device
+  // to assist error diagnosis.
+  int error_code_ = 0;
+  std::string error_message_;
+
   scoped_refptr<device::BluetoothAdapter> adapter_;
   scoped_refptr<device::BluetoothSocket> service_socket_;
   scoped_refptr<device::BluetoothSocket> controller_socket_;