Fix issues with protobuf equality comparisons

test/map_mixin_test.dart

Index: test/map_mixin_test.dart
diff --git a/test/map_mixin_test.dart b/test/map_mixin_test.dart
index 0fd974c5d919cc5a87ac24b7b2158c17dded307c..c7e6166e116c54fa6e78d0ae96dde6c8a56f4933 100644
--- a/test/map_mixin_test.dart
+++ b/test/map_mixin_test.dart
@@ -12,12 +12,12 @@ import 'dart:collection' show MapMixin;
 import 'package:protobuf/src/protobuf/mixins/map_mixin.dart';
 import 'package:test/test.dart' show test, expect, predicate, same, throws;
 
-import 'mock_util.dart' show MockMessage;
+import 'mock_util.dart' show MockMessage, mockInfo;
 
 // A minimal protobuf implementation compatible with PbMapMixin.
 class Rec extends MockMessage with MapMixin, PbMapMixin {
-  get className => "Rec";
-  Rec create() => new Rec();
+  get info_ => _info;
+  static final _info = mockInfo("Rec", () => new Rec());
 
   @override
   String toString() => "Rec(${val}, \"${str}\")";
@@ -65,4 +65,42 @@ main() {
     expect(r["int32s"], [123]);
     expect(r["int32s"], same(r["int32s"]));
   });
+
+  test('operator== and hashCode work for Map mixin', () {
+    var a = new Rec();
+    expect(a == a, true);
+    expect(a == {}, false);
+    expect({} == a, false);
+
+    var b = new Rec();
+    expect(a.info_ == b.info_, true, reason: "BuilderInfo should be the same");
+    expect(a == b, true);
+    expect(a.hashCode, b.hashCode);
+
+    a.val = 123;
+    expect(a == b, false);
+    b.val = 123;
+    expect(a == b, true);
+    expect(a.hashCode, b.hashCode);
+
+    a.child = new Rec();
+    expect(a == b, false);
+    b.child = new Rec();
+    expect(a == b, true);
+    expect(a.hashCode, b.hashCode);
+  });
+
+  test("protobuf doesn't compare equal to a map with the same values", () {
+    var a = new Rec();
+    expect(a == new Map.from(a), false);
+    expect(new Map.from(a) == a, false);
+  });
+
+  test("reading protobuf values shouldn't change equality", () {
+    var a = new Rec();
+    var b = new Rec();
+    expect(a == b, true);
+    new Map.from(a);
+    expect(a == b, true);
+  });
 }