Import wpt@40665266227e475bc4a56884247d8c09d78dfb6a

third_party/WebKit/LayoutTests/external/wpt/streams/piping/pipe-through.js

+'use strict';
+
+if (self.importScripts) {
+  self.importScripts('/resources/testharness.js');
+  self.importScripts('../resources/rs-utils.js');
+}
+
+function duckTypedPassThroughTransform() {
+  let enqueueInReadable;
+  let closeReadable;
+
+  return {
+    writable: new WritableStream({
+      write(chunk) {
+        enqueueInReadable(chunk);
+      },
+
+      close() {
+        closeReadable();
+      }
+    }),
+
+    readable: new ReadableStream({
+      start(c) {
+        enqueueInReadable = c.enqueue.bind(c);
+        closeReadable = c.close.bind(c);
+      }
+    })
+  };
+}
+
+promise_test(() => {
+  const readableEnd = sequentialReadableStream(5).pipeThrough(duckTypedPassThroughTransform());
+
+  return readableStreamToArray(readableEnd).then(chunks =>
+    assert_array_equals(chunks, [1, 2, 3, 4, 5]), 'chunks should match');
+}, 'Piping through a duck-typed pass-through transform stream should work');
+
+done();