Fix empty zlib deflate and early close of responses.

tests/standalone/io/http_compression_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 import 'dart:io';
 import 'dart:scalarlist';
 
 void testServerCompress() {
   void test(List<int> data) {
     HttpServer.bind().then((server) {
       server.listen((request) {
         request.response.writeBytes(data);
         request.response.close();
       });
       var client = new HttpClient();
       client.get("localhost", server.port, "/")
           .then((request) {
-            request.headers.set(HttpHeaders.ACCEPT_ENCODING, "gzip");
+            request.headers.set(HttpHeaders.ACCEPT_ENCODING, "gzip,deflate");
             return request.close();
           })
           .then((response) {
             Expect.equals("gzip",
                           response.headers.value(HttpHeaders.CONTENT_ENCODING));
             response
                 .transform(new ZLibInflater())
                 .reduce([], (list, b) {
                   list.addAll(b);
                   return list;
                 }).then((list) {
                   Expect.listEquals(data, list);
                   server.close();
                   client.close();
                 });
           });
     });
   }
   test("My raw server provided data".codeUnits);
   var longBuffer = new Uint8List(1024 * 1024);
   for (int i = 0; i < longBuffer.length; i++) {
     longBuffer[i] = i & 0xFF;
   }
   test(longBuffer);
 }
 
+void testAcceptEncodingHeader() {
+  void test(String encoding, bool valid) {
+    HttpServer.bind().then((server) {
+      server.listen((request) {
+        request.response.write("data");
+        request.response.close();
+      });
+      var client = new HttpClient();
+      client.get("localhost", server.port, "/")
+          .then((request) {
+            request.headers.set(HttpHeaders.ACCEPT_ENCODING, encoding);
+            return request.close();
+          })
+          .then((response) {
+            Expect.equals(
+              valid,
+              ("gzip" == response.headers.value(HttpHeaders.CONTENT_ENCODING)));
+            response.listen(
+                (_) {},
+                onDone: () {
+                  server.close();
+                  client.close();
+                });
+          });
+    });
+  }
+  test('gzip', true);
+  test('deflate', false);
+  test('gzip, deflate', true);
+  test('gzip ,deflate', true);
+  test('gzip  ,  deflate', true);
+  test('deflate,gzip', true);
+  test('deflate, gzip', true);
+  test('deflate ,gzip', true);
+  test('deflate  ,  gzip', true);
+  test('abc,deflate  ,  gzip,def,,,ghi  ,jkl', true);
+  test('xgzip', false);
+  test('gzipx;', false);
+}
+
 void main() {
   testServerCompress();
+  testAcceptEncodingHeader();
 }