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

sdk/lib/io/buffer_list.dart

Index: sdk/lib/io/buffer_list.dart
diff --git a/sdk/lib/io/buffer_list.dart b/sdk/lib/io/buffer_list.dart
index a369366b1f0334f79611a19d45e253f376a499c3..97e5e804012b288b45783db5de1c37c57df2405b 100644
--- a/sdk/lib/io/buffer_list.dart
+++ b/sdk/lib/io/buffer_list.dart
@@ -66,7 +66,8 @@ class _BufferList {
    * Read [count] bytes from the buffer list. If the number of bytes
    * requested is not available null will be returned.
    */
-  List<int> readBytes(int count) {
+  List<int> readBytes([int count]) {
+    if (count == null) count = length;
     List<int> result;
     if (_length == 0 || _length < count) return null;
     if (_index == 0 && _buffers.first.length == count) {