Fix Swarm to run again, and enable its test

frog/gen.dart

Index: frog/gen.dart
diff --git a/frog/gen.dart b/frog/gen.dart
index b6e8bf1e58708a5c42d99a77a460b70e49f330c7..011390ec62d0fbbfa013ca134beea4e81e8ae144 100644
--- a/frog/gen.dart
+++ b/frog/gen.dart
@@ -448,7 +448,7 @@ function $inheritsMembers(child, parent) {
       // [HashMapImplementation] which internally uses a constant expression.
       for (var global in list) {
         if (global.field == null) {
-          writer.writeln('${global.name} = ${global.exp.code};');
+          writer.writeln('var ${global.name} = ${global.exp.code};');
         }
       }
     }