Oops, broke dart2js. (Will be included in 0.3.9.)

Author: Brian Slesinsky

lib/src/protobuf/mixins/map_mixin.dart

@@ -11,7 +11,7 @@ import "package:protobuf/protobuf.dart" show BuilderInfo;
 ///
 /// This mixin is enabled via an option in
 /// dart_options.proto in dart-protoc-plugin.
-abstract class PbMapMixin implements Map<String, dynamic> {
+abstract class PbMapMixin implements Map {
 
   // GeneratedMessage properties and methods used by this mixin.