diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/PseudoPublisher.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/PseudoPublisher.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package jdk.incubator.http;
+
+import java.util.concurrent.Flow;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+// Completes the subscription on first request. Never calls onNext()
+
+class PseudoPublisher<T> implements Flow.Publisher<T> {
+
+    private final Throwable throwable;
+
+    PseudoPublisher() {
+        this(null);
+    }
+
+    PseudoPublisher(Throwable throwable) {
+        this.throwable = throwable;
+    }
+
+    @Override
+    public void subscribe(Flow.Subscriber<? super T> subscriber) {
+        subscriber.onSubscribe(new Subscription(subscriber));
+    }
+
+    private class Subscription implements Flow.Subscription {
+
+        private final Flow.Subscriber<? super T> subscriber;
+        private final AtomicBoolean done = new AtomicBoolean();
+
+        Subscription(Flow.Subscriber<? super T> subscriber) {
+            this.subscriber = subscriber;
+        }
+
+        @Override
+        public void request(long n) {
+            if (done.compareAndSet(false, true)) {
+                if (n > 0) {
+                    if (throwable == null) {
+                        subscriber.onComplete();
+                    } else {
+                        subscriber.onError(throwable);
+                    }
+                } else {
+                    subscriber.onError(new IllegalArgumentException("request(" + n + ")"));
+                }
+            }
+        }
+
+        @Override
+        public void cancel() {
+            done.set(true);
+        }
+
+    }
+}