sort classes in dependency order, or load lazily if needed, fixes #78

test/codegen/expect/dart/_js_helper.js

 var _js_helper;
 (function(exports) {
   'use strict';
   class NoSideEffects extends core.Object {
     NoSideEffects() {
     }
   }
   class NoThrows extends core.Object {
     NoThrows() {
     }
@@ skipping 1325 matching lines @@
   // Function requiresPreamble: () → dynamic
   function requiresPreamble() {
   }
   // Function isJsIndexable: (dynamic, dynamic) → bool
   function isJsIndexable(object, record) {
     if (record !== null) {
       let result = _interceptors.dispatchRecordIndexability(record);
       if (result !== null)
         return dart.as(result, core.bool);
     }
-    return dart.is(object, JavaScriptIndexingBehavior);
+    return dart.is(object, exports.JavaScriptIndexingBehavior);
   }
   // Function S: (dynamic) → String
   function S(value) {
     if (typeof value == string)
       return dart.as(value, core.String);
     if (dart.is(value, core.num)) {
       if (!dart.equals(value, 0)) {
         return "" + value;
       }
     } else if (true === value) {
@@ skipping 1769 matching lines @@
     if (value === null)
       return value;
     throw new TypeErrorImplementation.fromMessage(dart.as(message, core.String));
   }
   // Function checkDeferredIsLoaded: (String, String) → void
   function checkDeferredIsLoaded(loadId, uri) {
     if (!dart.notNull(exports._loadedLibraries.contains(loadId))) {
       throw new DeferredNotLoadedError(uri);
     }
   }
-  class JavaScriptIndexingBehavior extends _interceptors.JSMutableIndexable {
-  }
+  dart.defineLazyClass(exports, {
+    get JavaScriptIndexingBehavior() {
+      class JavaScriptIndexingBehavior extends _interceptors.JSMutableIndexable {
+      }
+      return JavaScriptIndexingBehavior;
+    }
+  });
   class TypeErrorImplementation extends core.Error {
     TypeErrorImplementation(value, type) {
       this.message = `type '${Primitives.objectTypeName(value)}' is not a subtype ` + `of type '${type}'`;
       super.Error();
     }
     TypeErrorImplementation$fromMessage(message) {
       this.message = message;
       super.Error();
     }
     toString() {
@@ skipping 800 matching lines @@
   exports.UnimplementedNoSuchMethodError = UnimplementedNoSuchMethodError;
   exports.random64 = random64;
   exports.jsonEncodeNative = jsonEncodeNative;
   exports.getIsolateAffinityTag = getIsolateAffinityTag;
   exports.loadDeferredLibrary = loadDeferredLibrary;
   exports.MainError = MainError;
   exports.missingMain = missingMain;
   exports.badMain = badMain;
   exports.mainHasTooManyParameters = mainHasTooManyParameters;
 })(_js_helper || (_js_helper = {}));