ClangTidy fixes

Change-Id: I188d6332c16f4c91bf92309e1eb524863e0c13ed

internal/ceres/autodiff_manifold_test.cc

diff --git a/internal/ceres/autodiff_manifold_test.cc b/internal/ceres/autodiff_manifold_test.cc
index f204d5a..b85d244 100644
--- a/internal/ceres/autodiff_manifold_test.cc
+++ b/internal/ceres/autodiff_manifold_test.cc
@@ -82,12 +82,12 @@
 }
 
 struct ScaledFunctor {
-  explicit ScaledFunctor(const double s) : s_(s) {}
+  explicit ScaledFunctor(const double s) : s(s) {}
 
   template <typename T>
   bool Plus(const T* x, const T* delta, T* x_plus_delta) const {
     for (int i = 0; i < 3; ++i) {
-      x_plus_delta[i] = x[i] + s_ * delta[i];
+      x_plus_delta[i] = x[i] + s * delta[i];
     }
     return true;
   }
@@ -95,12 +95,12 @@
   template <typename T>
   bool Minus(const T* y, const T* x, T* y_minus_x) const {
     for (int i = 0; i < 3; ++i) {
-      y_minus_x[i] = (y[i] - x[i]) / s_;
+      y_minus_x[i] = (y[i] - x[i]) / s;
     }
     return true;
   }
 
-  double s_;
+  const double s;
 };
 
 TEST(AutoDiffManifoldTest, ScaledManifold) {

internal/ceres/dense_cholesky.cc

diff --git a/internal/ceres/dense_cholesky.cc b/internal/ceres/dense_cholesky.cc
index 148c38c..f83fdf1 100644
--- a/internal/ceres/dense_cholesky.cc
+++ b/internal/ceres/dense_cholesky.cc
@@ -32,6 +32,7 @@
 
 #include <algorithm>
 #include <memory>
+#include <string>
 
 #ifndef CERES_NO_LAPACK
 
@@ -94,7 +95,7 @@
 LinearSolverTerminationType EigenDenseCholesky::Factorize(
     int num_cols, double* lhs, std::string* message) {
   Eigen::Map<Eigen::MatrixXd> m(lhs, num_cols, num_cols);
-  llt_.reset(new LLTType(m));
+  llt_ = std::make_unique<LLTType>(m);
   if (llt_->info() != Eigen::Success) {
     *message = "Eigen failure. Unable to perform dense Cholesky factorization.";
     return LINEAR_SOLVER_FAILURE;

internal/ceres/dense_cholesky_test.cc

diff --git a/internal/ceres/dense_cholesky_test.cc b/internal/ceres/dense_cholesky_test.cc
index 1b0ee65..eda4f10 100644
--- a/internal/ceres/dense_cholesky_test.cc
+++ b/internal/ceres/dense_cholesky_test.cc
@@ -32,6 +32,7 @@
 
 #include <memory>
 #include <numeric>
+#include <string>
 #include <vector>
 
 #include "Eigen/Dense"