QuadrupoleMomentIntegrand.hpp should add these lines:
class DataMesh;
template <class X> class Tensor;

QuadrupoleMomentIntegrand.hpp should remove these lines:
- #include "Utils/DataMesh/DataMesh.hpp"  // lines 8-8
- #include "Utils/Tensor/Tensor.hpp"  // lines 9-9

The full include-list for QuadrupoleMomentIntegrand.hpp:
#include <string>                       // for string
#include "Utils/DataBox/ComputeItem.hpp"
#include "Utils/DataBox/InstantiateDataBoxAdder.hpp"
class DataBoxAccess;  // lines 10-10
class DataMesh;
template <class X> class Tensor;
---

QuadrupoleMomentIntegrand.cpp should add these lines:
#include <stddef.h>                     // for size_t
#include "Utils/DataMesh/DataMesh.hpp"  // for DataMesh
#include "Utils/DataMesh/ExpressionTemplates.hpp"  // for BinaryOp, MultOp, etc
#include "Utils/ErrorHandling/MyErr.hpp"  // for operator<<
#include "Utils/Tensor/Tensor.hpp"      // for Tensor
#include "Utils/Tensor/TensorStructure.hpp"  // for TensorStructure, etc

QuadrupoleMomentIntegrand.cpp should remove these lines:

The full include-list for QuadrupoleMomentIntegrand.cpp:
#include "QuadrupoleMomentIntegrand.hpp"
#include <stddef.h>                     // for size_t
#include "Utils/DataBox/DataBoxAccess.hpp"  // for DataBoxAccess
#include "Utils/DataMesh/DataMesh.hpp"  // for DataMesh
#include "Utils/DataMesh/ExpressionTemplates.hpp"  // for BinaryOp, MultOp, etc
#include "Utils/DataMesh/Mesh.hpp"      // for Mesh, operator!=
#include "Utils/ErrorHandling/MyErr.hpp"  // for operator<<
#include "Utils/ErrorHandling/Require.hpp"  // for REQUIRE
#include "Utils/MiscUtils/SimpleProfiler.hpp"  // for SimpleProfiler
#include "Utils/MyContainers/MyVector.hpp"  // for MyVector, operator==
#include "Utils/StringParsing/OptionParser.hpp"  // for OptionParser
#include "Utils/Tensor/Tensor.hpp"      // for Tensor
#include "Utils/Tensor/TensorStructure.hpp"  // for TensorStructure, etc