WebKit export of https://bugs.webkit.org/show_bug.cgi?id=316159 (#60354)

Author: cdumez

fetch/api/request/request-clone-readable-stream-body.any.js

@@ -0,0 +1,22 @@
+// META: global=window,worker
+
+promise_test(async () => {
+    const stream = new ReadableStream({
+        start(controller) {
+            controller.enqueue(new TextEncoder().encode("hello"));
+            controller.close();
+        }
+    });
+
+    const r1 = new Request("https://example.com/", { method: "POST", body: stream, duplex: "half" });
+    const r2 = r1.clone();
+    assert_false(r2.bodyUsed, "clone should not be marked as used");
+    assert_not_equals(r2.body, null, "clone should have a body");
+
+    // Constructing a new Request from the clone should preserve the body.
+    const r3 = new Request(r2);
+    assert_not_equals(r3.body, null, "Request constructed from clone should have a body");
+
+    const text = await r3.text();
+    assert_equals(text, "hello", "body content should be preserved through clone() and new Request()");
+}, "new Request(clone) preserves a ReadableStream body that came from clone()");