ClangTidy fixes

Change-Id: I8d1a0258fc586040bd1cb5cc6131fdad2fe134eb

examples/bundle_adjuster.cc

diff --git a/examples/bundle_adjuster.cc b/examples/bundle_adjuster.cc
index 5b25d6f..2038885 100644
--- a/examples/bundle_adjuster.cc
+++ b/examples/bundle_adjuster.cc
@@ -65,6 +65,7 @@
 #include "absl/log/check.h"
 #include "absl/log/initialize.h"
 #include "absl/log/log.h"
+#include "absl/time/clock.h"
 #include "absl/time/time.h"
 #include "bal_problem.h"
 #include "ceres/ceres.h"

internal/ceres/problem_impl.cc

diff --git a/internal/ceres/problem_impl.cc b/internal/ceres/problem_impl.cc
index fb6f254..ef5851b 100644
--- a/internal/ceres/problem_impl.cc
+++ b/internal/ceres/problem_impl.cc
@@ -40,6 +40,7 @@
 #include <utility>
 #include <vector>
 
+#include "absl/container/btree_map.h"
 #include "absl/container/fixed_array.h"
 #include "absl/log/check.h"
 #include "absl/log/log.h"

internal/ceres/visibility.cc

diff --git a/internal/ceres/visibility.cc b/internal/ceres/visibility.cc
index 38fc6d9..bb3314d 100644
--- a/internal/ceres/visibility.cc
+++ b/internal/ceres/visibility.cc
@@ -38,6 +38,7 @@
 #include <vector>
 
 #include "absl/container/btree_set.h"
+#include "absl/container/flat_hash_map.h"
 #include "absl/log/check.h"
 #include "absl/log/log.h"
 #include "ceres/block_structure.h"