Check for duplicate library names

lib/runtime/dart/_js_helper.js

Index: lib/runtime/dart/_js_helper.js
diff --git a/lib/runtime/dart/_js_helper.js b/lib/runtime/dart/_js_helper.js
index b8873d8f3a4e4901e3f834cc151f3664ca90f7da..64e6f6ba8e8c076418f397a24be68300e2628f65 100644
--- a/lib/runtime/dart/_js_helper.js
+++ b/lib/runtime/dart/_js_helper.js
@@ -1,14 +1,15 @@
-var _js_helper = dart.defineLibrary(_js_helper, {});
-var core = dart.import(core);
-var collection = dart.import(collection);
-var _internal = dart.import(_internal);
-var _foreign_helper = dart.import(_foreign_helper);
-var _interceptors = dart.lazyImport(_interceptors);
-var _js_names = dart.import(_js_names);
-var _js_embedded_names = dart.import(_js_embedded_names);
-var async = dart.import(async);
-var _isolate_helper = dart.lazyImport(_isolate_helper);
-(function(exports, core, collection, _internal, _foreign_helper, _interceptors, _js_names, _js_embedded_names, async, _isolate_helper) {
+dart.library('dart/_js_helper.js', null, /* Imports */[
+  'dart/core.js',
+  'dart/collection.js',
+  'dart/_internal.js',
+  'dart/_foreign_helper.js',
+  'dart/_js_names.js',
+  'dart/_js_embedded_names.js',
+  'dart/async.js'
+], /* Lazy imports */[
+  'dart/_interceptors.js',
+  'dart/_isolate_helper.js'
+], function(exports, core, collection, _internal, _foreign_helper, _js_names, _js_embedded_names, async, _interceptors, _isolate_helper) {
   'use strict';
   class NoSideEffects extends core.Object {
     NoSideEffects() {
@@ -4160,4 +4161,4 @@ var _isolate_helper = dart.lazyImport(_isolate_helper);
   exports.missingMain = missingMain;
   exports.badMain = badMain;
   exports.mainHasTooManyParameters = mainHasTooManyParameters;
-})(_js_helper, core, collection, _internal, _foreign_helper, _interceptors, _js_names, _js_embedded_names, async, _isolate_helper);
+});