Implement create attribute API functions for BTLE.

device/bluetooth/test/mock_bluetooth_adapter.h

Index: device/bluetooth/test/mock_bluetooth_adapter.h
diff --git a/device/bluetooth/test/mock_bluetooth_adapter.h b/device/bluetooth/test/mock_bluetooth_adapter.h
index 4b3640937f7022a327adf0db80a3cb00e8c26a0d..a59674097a8992d4a592e0f78e829fbcecc0f334 100644
--- a/device/bluetooth/test/mock_bluetooth_adapter.h
+++ b/device/bluetooth/test/mock_bluetooth_adapter.h
@@ -98,6 +98,8 @@ class MockBluetoothAdapter : public BluetoothAdapter {
                void(const BluetoothAudioSink::Options& options,
                     const AcquiredCallback& callback,
                     const BluetoothAudioSink::ErrorCallback& error_callback));
+  MOCK_CONST_METHOD1(GetGattService,
+                     BluetoothLocalGattService*(const std::string& identifier));
 
   void StartDiscoverySessionWithFilter(
       std::unique_ptr<BluetoothDiscoveryFilter> discovery_filter,