Use a re-usable buffer for writing HTTP headers. This includes a new header limit of 8192 bytes.

tests/standalone/io/http_client_request_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.
 
 import "dart:async";
 import "dart:io";
 import "dart:typed_data";
 
 import "package:async_helper/async_helper.dart";
 import "package:expect/expect.dart";
 
+
 void testClientRequest(Future handler(request)) {
   HttpServer.bind("127.0.0.1", 0).then((server) {
     server.listen((request) {
       request.drain()
           .then((_) => request.response.close())
           .catchError((_) {});
     });
 
     var client = new HttpClient();
     client.get("127.0.0.1", server.port, "/")
       .then((request) {
         return handler(request);
       })
       .then((response) => response.drain())
       .catchError((_) {})
       .whenComplete(() {
         client.close();
         server.close();
       });
   });
 }
 
+
 void testResponseDone() {
   testClientRequest((request) {
     request.close().then((res1) {
       request.done.then((res2) {
         Expect.equals(res1, res2);
       });
     });
     return request.done;
   });
 }
 
+
 void testBadResponseAdd() {
   asyncStart();
   testClientRequest((request) {
     request.contentLength = 0;
     request.add([0]);
     request.close();
     request.done.catchError((error) {
       asyncEnd();
     }, test: (e) => e is HttpException);
     return request.done;
@@ skipping 18 matching lines @@
     request.add(new Uint8List(64 * 1024));
     request.add(new Uint8List(64 * 1024));
     request.close();
     request.done.catchError((error) {
       asyncEnd();
     }, test: (e) => e is HttpException);
     return request.done;
   });
 }
 
+
 void testBadResponseClose() {
   asyncStart();
   testClientRequest((request) {
     request.contentLength = 5;
     request.close();
     request.done.catchError((error) {
       asyncEnd();
     }, test: (e) => e is HttpException);
     return request.done;
   });
 
   asyncStart();
   testClientRequest((request) {
     request.contentLength = 5;
     request.add([0]);
     request.close();
     request.done.catchError((error) {
       asyncEnd();
     }, test: (e) => e is HttpException);
     return request.done;
   });
 }
 
+
+void testBadHeaders() {
+  asyncStart();
+  testClientRequest((request) {
+    var value = "a";
+    for (int i = 0; i < 8 * 1024; i++) {
+      value += 'a';
+    }
+    request.headers.set('name', value);
+    request.done.catchError((error) {
+      asyncEnd();
+    }, test: (e) => e is HttpException);
+    return request.close();
+  });
+}
+
+
 void main() {
   testResponseDone();
   testBadResponseAdd();
   testBadResponseClose();
+  testBadHeaders();
 }