bary_by_value.patch

diff --git a/math/barycentric.cc b/math/barycentric.cc
index d4ba892..92f4fd6 100644
--- a/math/barycentric.cc
+++ b/math/barycentric.cc
@@ -14,19 +14,19 @@ namespace drake {
 namespace math {
 
 template <typename T>
-BarycentricMesh<T>::BarycentricMesh(std::unique_ptr<MeshGrid> input_grid)
+BarycentricMesh<T>::BarycentricMesh(MeshGrid input_grid)
     : input_grid_(std::move(input_grid)),
-      stride_(input_grid_->size()),
+      stride_(input_grid_.size()),
       num_interpolants_{1} {
-  DRAKE_DEMAND(input_grid_->size() > 0);
+  DRAKE_DEMAND(input_grid_.size() > 0);
   for (int i = 0; i < get_num_inputs(); i++) {
     // Must define at least one mesh point per dimension.
-    DRAKE_DEMAND(!input_grid_->at(i).empty());
+    DRAKE_DEMAND(!input_grid_.at(i).empty());
 
     // Gain one interpolant for every non-singleton dimension
-    if (input_grid_->at(i).size() > 1) num_interpolants_++;
+    if (input_grid_.at(i).size() > 1) num_interpolants_++;
 
-    stride_[i] = (i == 0) ? 1 : input_grid_->at(i - 1).size() * stride_[i - 1];
+    stride_[i] = (i == 0) ? 1 : input_grid_.at(i - 1).size() * stride_[i - 1];
   }
 }
 
@@ -38,9 +38,9 @@ void BarycentricMesh<T>::get_mesh_point(int index,
   // Iterate through the input dimensions, assigning the value and reducing
   // the index to be relevant only to the remaining dimensions.
   for (int i = 0; i < get_num_inputs(); i++) {
-    const auto& coords = input_grid_->at(i);
+    const auto& coords = input_grid_.at(i);
     int dim_index = index % coords.size();
-    (*point)[i] = *(std::next(input_grid_->at(i).begin(), dim_index));
+    (*point)[i] = *(std::next(input_grid_.at(i).begin(), dim_index));
     index /= coords.size();  // intentionally truncate to int.
   }
   DRAKE_DEMAND(index == 0);  // otherwise the index was out of range.
@@ -63,7 +63,7 @@ void BarycentricMesh<T>::EvalBarycentricWeights(
   // indices.  Set current_index to the "top right" corner index.
   int count = 0;
   for (int i = 0; i < get_num_inputs(); i++) {
-    const auto& coords = input_grid_->at(i);
+    const auto& coords = input_grid_.at(i);
 
     // Skip over singleton dimensions.
     if (coords.size() == 1) continue;
diff --git a/math/barycentric.h b/math/barycentric.h
index 5136ace..469f119 100644
--- a/math/barycentric.h
+++ b/math/barycentric.h
@@ -54,13 +54,13 @@ class BarycentricMesh {
   typedef std::vector<Coordinates> MeshGrid;
 
   /// Constructs the mesh.
-  explicit BarycentricMesh(std::unique_ptr<MeshGrid> input_grid);
+  explicit BarycentricMesh(MeshGrid input_grid);
 
   /// Accessor methods.
-  int get_num_inputs() const { return input_grid_->size(); }
+  int get_num_inputs() const { return input_grid_.size(); }
   int get_num_mesh_points() const {
     int num_mesh_points = 1;
-    for (const auto& coords : *input_grid_) {
+    for (const auto& coords : input_grid_) {
       num_mesh_points *= coords.size();
     }
     return num_mesh_points;
@@ -105,9 +105,8 @@ class BarycentricMesh {
             EigenPtr<VectorX<T>> output) const;
 
  private:
-  const std::unique_ptr<MeshGrid> input_grid_;  // Specifies the location of the
-                                                // mesh points in the input
-                                                // space.
+  const MeshGrid input_grid_;  // Specifies the location of the mesh points in
+                               // the input space.
   std::vector<int> stride_;  // The number of elements to skip to arrive at the
                              // next value (per input dimension)
   int num_interpolants_{1};  // The number of points used in any interpolation.
diff --git a/math/test/barycentric_test.cc b/math/test/barycentric_test.cc
index b92aaa8..99cbf04 100644
--- a/math/test/barycentric_test.cc
+++ b/math/test/barycentric_test.cc
@@ -24,14 +24,12 @@ GTEST_TEST(BarycentricTest, GetMeshPoints) {
   // Create a mesh in 3 (input) dimensions, with the second dimension being a
   // singleton.
   const int kNumInputs = 3;
-  auto grid = std::make_unique<BarycentricMesh<double>::MeshGrid>(kNumInputs);
-
-  // Setup the input mesh by specifying the grid one dimension at at time.
-  grid->at(0) = {0.0, 1.0};
-  grid->at(1) = {2.0};
-  grid->at(2) = {3.0, 4.0};
+  BarycentricMesh<double> bary{{
+      {0.0, 1.0},  // BR
+      {2.0},       // BR
+      {3.0, 4.0},  // BR
+  }};
 
-  BarycentricMesh<double> bary(std::move(grid));
   EXPECT_EQ(bary.get_num_inputs(), kNumInputs);
   EXPECT_EQ(bary.get_num_mesh_points(), 4);
 
@@ -51,15 +49,11 @@ GTEST_TEST(BarycentricTest, GetMeshPoints) {
 GTEST_TEST(BarycentricTest, EvalWeights) {
   // Create a mesh in 3 (input) dimensions, with the second dimension being a
   // singleton.
-  const int kNumInputs = 3;
-  auto grid = std::make_unique<BarycentricMesh<double>::MeshGrid>(kNumInputs);
-
-  // Setup the input mesh by specifying the grid one dimension at at time.
-  grid->at(0) = {0.0, 1.0};
-  grid->at(1) = {2.0};
-  grid->at(2) = {3.0, 4.0};
-
-  BarycentricMesh<double> bary(std::move(grid));
+  BarycentricMesh<double> bary{{
+      {0.0, 1.0},  // BR
+      {2.0},       // BR
+      {3.0, 4.0},  // BR
+  }};
 
   VectorXi indices(3);
   VectorXd weights(3);
@@ -101,14 +95,10 @@ GTEST_TEST(BarycentricTest, EvalWeights) {
 }
 
 GTEST_TEST(BarycentricTest, EvalTest) {
-  const int kNumInputs = 2;
-  auto grid = std::make_unique<BarycentricMesh<double>::MeshGrid>(kNumInputs);
-
-  // Setup the input mesh by specifying the grid one dimension at at time.
-  grid->at(0) = {0.0, 1.0};
-  grid->at(1) = {0.0, 1.0};
-
-  BarycentricMesh<double> bary(std::move(grid));
+  BarycentricMesh<double> bary{{
+      {0.0, 1.0},  // BR
+      {0.0, 1.0},  // BR
+  }};
 
   MatrixXd mesh = Eigen::RowVector4d{1., 2., 3., 4.};
 
@@ -144,11 +134,10 @@ GTEST_TEST(BarycentricTest, MultidimensionalOutput) {
   const int kNumInputs = 2;
   auto grid = std::make_unique<BarycentricMesh<double>::MeshGrid>(kNumInputs);
 
-  // Setup the input mesh by specifying the grid one dimension at at time.
-  grid->at(0) = {0.0, 1.0};
-  grid->at(1) = {0.0, 1.0};
-
-  BarycentricMesh<double> bary(std::move(grid));
+  BarycentricMesh<double> bary{{
+      {0.0, 1.0},  // BR
+      {0.0, 1.0},  // BR
+  }};
 
   const int kNumOutputs = 2;
   MatrixXd mesh(kNumOutputs, bary.get_num_mesh_points());