message: Add const qualifiers whenever appropriate.
diff: @@ -93,7 +93,7 @@ Status AddImages(const string& tag, int max_images, int batch_size, int w,
  v->set_tag(strings::StrCat(tag, "/image"));
  }
  - auto image = ith_image(i);
  + const auto image = ith_image(i);
  Summary::Image* si = v->mutable_image();
  si->set_height(h);
  si->set_width(w);
  @@ -154,7 +154,7 @@ void NormalizeFloatImage(int hw, int depth,
  const float kZeroThreshold = 1e-6;
  T scale, offset;
  if (image_min < 0) {
  - float max_val = std::max(std::abs(image_min), std::abs(image_max));
  + const float max_val = std::max(std::abs(image_min), std::abs(image_max));
  scale = T(max_val < kZeroThreshold ? 0.0f : 127.0f / max_val);
  offset = T(128.0f);
  } else {
  @@ -217,7 +217,7 @@ class SummaryWriterImpl : public SummaryWriterInterface {
  Status Initialize(const string& logdir, const string& filename_suffix,
  Env* env) {
  - Status is_dir = env->IsDirectory(logdir);
  + const Status is_dir = env->IsDirectory(logdir);
  if (!is_dir.ok()) {
  if (is_dir.code() != tensorflow::error::NOT_FOUND) {
  return is_dir;
  @@ -419,7 +419,7 @@ Status CreateSummaryWriter(int max_queue, int flush_millis,
  const string& logdir, const string& filename_suffix,
  Env* env, SummaryWriterInterface** result) {
  SummaryWriterImpl* w = new SummaryWriterImpl(max_queue, flush_millis);
  - Status s = w->Initialize(logdir, filename_suffix, env);
  + const Status s = w->Initialize(logdir, filename_suffix, env);
  if (!s.ok()) {
  w->Unref();
  *result = nullptr;
  