Make HTTP headers use a growing buffer, not a fixed-size 8K one.

tests/standalone/io/http_server_response_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
 // OtherResources=http_server_response_test.dart
 
@@ skipping 263 matching lines @@
                   .fold(0, (s, b) => s + b.length)
                   .then((bytes) {
                     Expect.equals(8, bytes);
                     server.close();
                   });
             });
       });
 }
 
 
-void testBadHeaders() {
-  testServerRequest((server, request) {
-    var value = "a";
-    for (int i = 0; i < 8 * 1024; i++) {
-      value += 'a';
-    }
-    request.response.headers.set('name', value);
-    request.response.close().catchError((error) {
-      server.close();
-    }, test: (e) => e is HttpException);
-  });
-}
-
-
 void testWriteCharCode() {
   testServerRequest((server, request) {
     // Test that default is latin-1 (only 2 bytes).
     request.response.writeCharCode(0xFF);
     request.response.writeCharCode(0xFF);
     request.response.close().then((_) {
       server.close();
     });
   }, bytes: 2);
 }
 
 
 void main() {
   testResponseDone();
   testResponseAddStream();
   testResponseAddStreamClosed();
   testResponseAddClosed();
   testBadResponseAdd();
   testBadResponseClose();
   testIgnoreRequestData();
-  testBadHeaders();
   testWriteCharCode();
 }