Update hashCode to hash the entire message

lib/pb_list.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of protobuf;
 
 class PbList<E> extends Object with ListMixin<E> implements List<E> {
 
   PbList() : _wrappedList = <E>[];
 
   PbList.from(List from) : _wrappedList = new List<E>.from(from);
 
   bool operator ==(other) =>
       (other is PbList) && _areListsEqual(other, this);
 
-  int get hashCode => _wrappedList.hashCode;
+  int get hashCode {
+    int hash = 0;
+    _wrappedList.forEach((value) {
+      hash = (hash + value.hashCode) & 0x3fffffff;
+      hash = (hash + hash << 10) & 0x3fffffff;
+      hash = (hash ^ hash >> 6) & 0x3fffffff;
+    });
+    hash = (hash + hash << 3) & 0x3fffffff;
+    hash = (hash ^ hash >> 11) & 0x3fffffff;
+    hash = (hash + hash << 15) & 0x3fffffff;
+    return hash;
+  }
 
   /**
    * Returns an [Iterator] for the list.
    */
   Iterator<E> get iterator => _wrappedList.iterator;
 
   /**
    * Returns the element at the given [index] in the list or throws
    * an [IndexOutOfRangeException] if [index] is out of bounds.
    */
@@ skipping 162 matching lines @@
  * [:-3.4E38, 3.4E38:], i.e., with the IEEE single-precision range.
  */
 class PbFloatList extends PbList<double> {
   void _validateElement(double val) {
     if (!_isFloat32(val)) {
       throw new ArgumentError('Illegal to add value (${val}):'
           ' out of range for float');
     }
   }
 }