Adding std::ostream& operator<<(std::ostream& out, NSError* error)

device/bluetooth/bluetooth_adapter_mac.h

Index: device/bluetooth/bluetooth_adapter_mac.h
diff --git a/device/bluetooth/bluetooth_adapter_mac.h b/device/bluetooth/bluetooth_adapter_mac.h
index 2dd3a3f53fed836bec4bd2810d6fbf1c3fe7949d..543d1953d8cc19b7dc20e7f703b92a6fd4888590 100644
--- a/device/bluetooth/bluetooth_adapter_mac.h
+++ b/device/bluetooth/bluetooth_adapter_mac.h
@@ -229,6 +229,10 @@ class DEVICE_BLUETOOTH_EXPORT BluetoothAdapterMac
   DISALLOW_COPY_AND_ASSIGN(BluetoothAdapterMac);
 };
 
+// Stream operator for logging.
+DEVICE_BLUETOOTH_EXPORT std::ostream& operator<<(std::ostream& out,
+                                                 NSError* error);
+
 }  // namespace device
 
 #endif  // DEVICE_BLUETOOTH_BLUETOOTH_ADAPTER_MAC_H_