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

tests/standalone/io/http_client_request_test.dart

Index: tests/standalone/io/http_client_request_test.dart
diff --git a/tests/standalone/io/http_client_request_test.dart b/tests/standalone/io/http_client_request_test.dart
index 9015b9f4abf46eb58162ff88e6fad13952bcb6ea..cd2a7beb045adca865c1232f7cea83fe1780d193 100644
--- a/tests/standalone/io/http_client_request_test.dart
+++ b/tests/standalone/io/http_client_request_test.dart
@@ -108,25 +108,8 @@ void testBadResponseClose() {
 }
 
 
-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();
 }