Fix the ceres.bzl to add missing cc files.

Thanks to nate-thirdwave@ for pointing this out and offering
a fix.

Also add a TODO about an odd loop in covariance_impl.cc which was
revealed as I was testing the bazel build

https: //github.com/ceres-solver/ceres-solver/issues/800
Change-Id: I87d17155ee43ea2a52b8031177d6b3ac5ae1460a
diff --git a/bazel/ceres.bzl b/bazel/ceres.bzl
index fad2754..c76e23a 100644
--- a/bazel/ceres.bzl
+++ b/bazel/ceres.bzl
@@ -32,8 +32,8 @@
     "accelerate_sparse.cc",
     "array_utils.cc",
     "block_evaluate_preparer.cc",
-    "block_jacobian_writer.cc",
     "block_jacobi_preconditioner.cc",
+    "block_jacobian_writer.cc",
     "block_random_access_dense_matrix.cc",
     "block_random_access_diagonal_matrix.cc",
     "block_random_access_matrix.cc",
@@ -53,10 +53,13 @@
     "context_impl.cc",
     "coordinate_descent_minimizer.cc",
     "corrector.cc",
+    "cost_function.cc",
     "covariance.cc",
     "covariance_impl.cc",
+    "cxsparse.cc",
     "dense_cholesky.cc",
     "dense_normal_cholesky_solver.cc",
+    "dense_qr.cc",
     "dense_qr_solver.cc",
     "dense_sparse_matrix.cc",
     "detect_structure.cc",
@@ -65,25 +68,30 @@
     "dynamic_compressed_row_sparse_matrix.cc",
     "dynamic_sparse_normal_cholesky_solver.cc",
     "eigensparse.cc",
+    "evaluation_callback.cc",
     "evaluator.cc",
     "file.cc",
+    "first_order_function.cc",
+    "float_cxsparse.cc",
+    "float_suitesparse.cc",
     "function_sample.cc",
     "gradient_checker.cc",
     "gradient_checking_cost_function.cc",
     "gradient_problem.cc",
     "gradient_problem_solver.cc",
-    "is_close.cc",
     "implicit_schur_complement.cc",
     "inner_product_computer.cc",
+    "is_close.cc",
+    "iteration_callback.cc",
     "iterative_refiner.cc",
     "iterative_schur_complement_solver.cc",
     "levenberg_marquardt_strategy.cc",
     "line_search.cc",
     "line_search_direction.cc",
     "line_search_minimizer.cc",
+    "line_search_preprocessor.cc",
     "linear_least_squares_problems.cc",
     "linear_operator.cc",
-    "line_search_preprocessor.cc",
     "linear_solver.cc",
     "local_parameterization.cc",
     "loss_function.cc",
@@ -92,6 +100,7 @@
     "minimizer.cc",
     "normal_prior.cc",
     "parallel_for_cxx.cc",
+    "parallel_for_nothreads.cc",
     "parallel_for_openmp.cc",
     "parallel_utils.cc",
     "parameter_block_ordering.cc",
diff --git a/internal/ceres/covariance_impl.cc b/internal/ceres/covariance_impl.cc
index 15a454f..d6ce69b 100644
--- a/internal/ceres/covariance_impl.cc
+++ b/internal/ceres/covariance_impl.cc
@@ -480,6 +480,9 @@
     // Iterate over the covariance blocks contained in this row block
     // and count the number of columns in this row block.
     int num_col_blocks = 0;
+
+    // TODO(sameeragarwal): num_columns is being computed but not
+    // being used.
     int num_columns = 0;
     for (int j = i; j < covariance_blocks.size(); ++j, ++num_col_blocks) {
       const std::pair<const double*, const double*>& block_pair =