Check for duplicate library names

lib/runtime/dart/_js_names.js

Index: lib/runtime/dart/_js_names.js
diff --git a/lib/runtime/dart/_js_names.js b/lib/runtime/dart/_js_names.js
index ae22d851269453216709aa0f1f9201a461ec8e40..800248004bf47540e2d3a1aa71f6b766317ec8c8 100644
--- a/lib/runtime/dart/_js_names.js
+++ b/lib/runtime/dart/_js_names.js
@@ -1,10 +1,11 @@
-var _js_names = dart.defineLibrary(_js_names, {});
-var _foreign_helper = dart.lazyImport(_foreign_helper);
-var _js_embedded_names = dart.import(_js_embedded_names);
-var core = dart.import(core);
-var _interceptors = dart.import(_interceptors);
-var _js_helper = dart.lazyImport(_js_helper);
-(function(exports, _foreign_helper, _js_embedded_names, core, _interceptors, _js_helper) {
+dart.library('dart/_js_names.js', null, /* Imports */[
+  'dart/_js_embedded_names.js',
+  'dart/core.js',
+  'dart/_interceptors.js'
+], /* Lazy imports */[
+  'dart/_foreign_helper.js',
+  'dart/_js_helper.js'
+], function(exports, _js_embedded_names, core, _interceptors, _foreign_helper, _js_helper) {
   'use strict';
   function preserveNames() {
   }
@@ -81,4 +82,4 @@ var _js_helper = dart.lazyImport(_js_helper);
   exports.extractKeys = extractKeys;
   exports.unmangleGlobalNameIfPreservedAnyways = unmangleGlobalNameIfPreservedAnyways;
   exports.unmangleAllIdentifiersIfPreservedAnyways = unmangleAllIdentifiersIfPreservedAnyways;
-})(_js_names, _foreign_helper, _js_embedded_names, core, _interceptors, _js_helper);
+});