Fetch: add test for cloning Request/Response body input

fetch/api/body/cloned-any.js

@@ -0,0 +1,50 @@
+// Changing the body after it have been passed to Response/Request
+// should not change the outcome of the consumed body
+
+const url = 'http://a';
+const method = 'post';
+
+promise_test(async t => {
+  const body = new FormData();
+  body.set('a', '1');
+  const res = new Response(body);
+  const req = new Request(url, { method, body });
+  body.set('a', '2');
+  assert_true((await res.formData()).get('a') === '1');
+  assert_true((await req.formData()).get('a') === '1');
+}, 'FormData is cloned');
+
+promise_test(async t => {
+  const body = new URLSearchParams({a: '1'});
+  const res = new Response(body);
+  const req = new Request(url, { method, body });
+  body.set('a', '2');
+  assert_true((await res.formData()).get('a') === '1');
+  assert_true((await req.formData()).get('a') === '1');
+}, 'URLSearchParams is cloned');
+
+promise_test(async t => {
+  const body = new Uint8Array([97]); // a
+  const res = new Response(body);
+  const req = new Request(url, { method, body });
+  body[0] = 98; // b
+  assert_true(await res.text() === 'a');
+  assert_true(await req.text() === 'a');
+}, 'TypedArray is cloned');
+
+promise_test(async t => {
+  const body = new Uint8Array([97]); // a
+  const res = new Response(body.buffer);
+  const req = new Request(url, { method, body: body.buffer });
+  body[0] = 98; // b
+  assert_true(await res.text() === 'a');
+  assert_true(await req.text() === 'a');
+}, 'ArrayBuffer is cloned');
+
+promise_test(async t => {
+  const body = new Blob(['a']);
+  const res = new Response(body);
+  const req = new Request(url, { method, body });
+  assert_true(await res.blob() !== body);
+  assert_true(await req.blob() !== body);
+}, 'Blob is cloned');