Add DBus plumbing and tests for sending devices with ATT read/writes.

device/bluetooth/bluez/bluetooth_local_gatt_service_bluez.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DEVICE_BLUETOOTH_BLUEZ_BLUETOOTH_LOCAL_GATT_SERVICE_BLUEZ_H_
 #define DEVICE_BLUETOOTH_BLUEZ_BLUETOOTH_LOCAL_GATT_SERVICE_BLUEZ_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 42 matching lines @@
                   const ErrorCallback& error_callback) override;
   bool IsRegistered() override;
   void Delete() override;
   device::BluetoothLocalGattCharacteristic* GetCharacteristic(
       const std::string& identifier) override;
 
   const std::map<dbus::ObjectPath,
                  std::unique_ptr<BluetoothLocalGattCharacteristicBlueZ>>&
   GetCharacteristics() const;
 
-  Delegate* GetDelegate() { return delegate_; }
+  Delegate* GetDelegate() const { return delegate_; }
 
   static dbus::ObjectPath AddGuidToObjectPath(const std::string& path);
 
  private:
   friend class BluetoothLocalGattCharacteristicBlueZ;
   // Needs access to weak_ptr_factory_.
   friend class device::BluetoothLocalGattService;
 
   // Called by dbus:: on unsuccessful completion of a request to register a
   // local service.
@@ skipping 22 matching lines @@
   // Note: This should remain the last member so it'll be destroyed and
   // invalidate its weak pointers before any other members are destroyed.
   base::WeakPtrFactory<BluetoothLocalGattServiceBlueZ> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BluetoothLocalGattServiceBlueZ);
 };
 
 }  // namespace bluez
 
 #endif  // DEVICE_BLUETOOTH_BLUEZ_BLUETOOTH_LOCAL_GATT_SERVICE_BLUEZ_H_