Bring in latest dart:io WebSocket code.

lib/src/copy/bytes_builder.dart

Index: lib/src/copy/bytes_builder.dart
diff --git a/lib/src/bytes_builder.dart b/lib/src/copy/bytes_builder.dart
similarity index 97%
rename from lib/src/bytes_builder.dart
rename to lib/src/copy/bytes_builder.dart
index 68af4170bdcea2db4873a75727892edc44cf79cb..4ab83b369519fcbc1735c3fe5295a8bae4c0a07d 100644
--- a/lib/src/bytes_builder.dart
+++ b/lib/src/copy/bytes_builder.dart
@@ -7,7 +7,10 @@
 // non-"dart:io" applications (issue 18348).
 //
 // Because it's copied directly, there are no modifications from the original.
-library http_parser.bytes_builder;
+//
+// This is up-to-date as of sdk revision
+// 86227840d75d974feb238f8b3c59c038b99c05cf.
+library http_parser.copy.bytes_builder;
 
 import 'dart:math';
 import 'dart:typed_data';
@@ -86,6 +89,7 @@ abstract class BytesBuilder {
   void clear();
 }
 
+
 class _CopyingBytesBuilder implements BytesBuilder {
   // Start with 1024 bytes.
   static const int _INIT_SIZE = 1024;
@@ -157,6 +161,7 @@ class _CopyingBytesBuilder implements BytesBuilder {
   }
 }
 
+
 class _BytesBuilder implements BytesBuilder {
   int _length = 0;
   final List _chunks = [];