fixes #427, static fields emitted outside the scope of their class

test/codegen/expect/es6_modules.js

 const exports = {};
 import dart from "./dart/_runtime";
 import core from "./dart/core";
 let dartx = dart.dartx;
 const Callback = dart.typedef('Callback', () => dart.functionType(dart.void, [], {i: core.int}));
 class A extends core.Object {}
 class _A extends core.Object {}
 const B$ = dart.generic(function(T) {
   class B extends core.Object {}
   return B;
 });
 let B = B$();
 const _B$ = dart.generic(function(T) {
   class _B extends core.Object {}
   return _B;
 });
 let _B = _B$();
 function f() {
 }
 dart.fn(f);
 function _f() {
 }
 dart.fn(_f);
 const constant = "abc";
 exports.finalConstant = "abc";
-exports.mutable = "abc";
 dart.defineLazyProperties(exports, {
   get lazy() {
     return dart.as(dart.fn(() => {
       core.print('lazy');
       return "abc";
     })(), core.String);
-  },
+  }
+});
+exports.mutable = "abc";
+dart.defineLazyProperties(exports, {
   get lazyMutable() {
     return dart.as(dart.fn(() => {
       core.print('lazyMutable');
       return "abc";
     })(), core.String);
   },
   set lazyMutable(_) {}
 });
 // Exports:
 exports.Callback = Callback;
 exports.A = A;
 exports.B$ = B$;
 exports.B = B;
 exports.f = f;
 exports.constant = constant;
 export default exports;