Vendor dependencies

Let's see how I like this workflow.

vendor/chrono/benches/serde.rs

@@ -0,0 +1,29 @@
+#![cfg(feature = "__internal_bench")]
+
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+
+use chrono::NaiveDateTime;
+
+fn bench_ser_naivedatetime_string(c: &mut Criterion) {
+    c.bench_function("bench_ser_naivedatetime_string", |b| {
+        let dt: NaiveDateTime = "2000-01-01T00:00:00".parse().unwrap();
+        b.iter(|| {
+            black_box(serde_json::to_string(&dt)).unwrap();
+        });
+    });
+}
+
+fn bench_ser_naivedatetime_writer(c: &mut Criterion) {
+    c.bench_function("bench_ser_naivedatetime_writer", |b| {
+        let mut s: Vec<u8> = Vec::with_capacity(20);
+        let dt: NaiveDateTime = "2000-01-01T00:00:00".parse().unwrap();
+        b.iter(|| {
+            let s = &mut s;
+            s.clear();
+            black_box(serde_json::to_writer(s, &dt)).unwrap();
+        });
+    });
+}
+
+criterion_group!(benches, bench_ser_naivedatetime_writer, bench_ser_naivedatetime_string);
+criterion_main!(benches);