Change new List(n) to return fixed length list.

sdk/lib/io/websocket_impl.dart

Index: sdk/lib/io/websocket_impl.dart
diff --git a/sdk/lib/io/websocket_impl.dart b/sdk/lib/io/websocket_impl.dart
index a77ebfa730f3874c19dd06196e38d6925b19e4e1..6c3f13ea5e91fbe9859916a01282b5134c72c0d0 100644
--- a/sdk/lib/io/websocket_impl.dart
+++ b/sdk/lib/io/websocket_impl.dart
@@ -447,7 +447,7 @@ class _WebSocketImpl extends Stream<Event> implements WebSocket {
 
     Random random = new Random();
     // Generate 16 random bytes.
-    List<int> nonceData = new List<int>.fixedLength(16);
+    List<int> nonceData = new List<int>(16);
     for (int i = 0; i < 16; i++) {
       nonceData[i] = random.nextInt(256);
     }
@@ -640,7 +640,7 @@ class _WebSocketImpl extends Stream<Event> implements WebSocket {
     } else if (dataLength > 125) {
       headerSize += 2;
     }
-    List<int> header = new List<int>.fixedLength(headerSize);
+    List<int> header = new List<int>(headerSize);
     int index = 0;
     // Set FIN and opcode.
     header[index++] = 0x80 | opcode;