bluetooth: Save characteristic value when notification arrives

device/bluetooth/test/test_bluetooth_adapter_observer.h

Index: device/bluetooth/test/test_bluetooth_adapter_observer.h
diff --git a/device/bluetooth/test/test_bluetooth_adapter_observer.h b/device/bluetooth/test/test_bluetooth_adapter_observer.h
index d41d1d24641ee024d88a72c448a6cb8bf2c9b737..683466010f0757d6e73b791620751addb0edeb2e 100644
--- a/device/bluetooth/test/test_bluetooth_adapter_observer.h
+++ b/device/bluetooth/test/test_bluetooth_adapter_observer.h
@@ -143,6 +143,10 @@ class TestBluetoothAdapterObserver : public BluetoothAdapter::Observer {
   std::vector<uint8_t> last_changed_characteristic_value() const {
     return last_changed_characteristic_value_;
   }
+  std::vector<std::vector<uint8_t>>
+  previous_characteristic_value_changed_values() const {
+    return previous_characteristic_value_changed_values_;
+  }
   std::string last_gatt_descriptor_id() const {
     return last_gatt_descriptor_id_;
   }
@@ -198,6 +202,8 @@ class TestBluetoothAdapterObserver : public BluetoothAdapter::Observer {
   std::string last_gatt_characteristic_id_;
   BluetoothUUID last_gatt_characteristic_uuid_;
   std::vector<uint8_t> last_changed_characteristic_value_;
+  std::vector<std::vector<uint8_t>>
+      previous_characteristic_value_changed_values_;
   std::string last_gatt_descriptor_id_;
   BluetoothUUID last_gatt_descriptor_uuid_;
   std::vector<uint8_t> last_changed_descriptor_value_;