Buffer the entire http header to one packet, and buffer other data in chunks of 4-16 kb.

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 d2c9236c446109448b1e291e164cbac07759cd6d..84e7b2dd4f40cf0e20ec99bbba18af5d1f6a4345 100644
--- a/tests/standalone/io/http_client_request_test.dart
+++ b/tests/standalone/io/http_client_request_test.dart
@@ -47,6 +47,7 @@ void testBadResponseAdd() {
     var port = new ReceivePort();
     request.contentLength = 0;
     request.writeBytes([0]);
+    request.close();
     request.done.catchError((error) {
       port.close();
     }, test: (e) => e is HttpException);
@@ -58,6 +59,7 @@ void testBadResponseAdd() {
     request.contentLength = 5;
     request.writeBytes([0, 0, 0]);
     request.writeBytes([0, 0, 0]);
+    request.close();
     request.done.catchError((error) {
       port.close();
     }, test: (e) => e is HttpException);
@@ -70,6 +72,7 @@ void testBadResponseAdd() {
     request.writeBytes(new Uint8List(64 * 1024));
     request.writeBytes(new Uint8List(64 * 1024));
     request.writeBytes(new Uint8List(64 * 1024));
+    request.close();
     request.done.catchError((error) {
       port.close();
     }, test: (e) => e is HttpException);