Check for duplicate library names

lib/runtime/dart/core.js

-var core = dart.defineLibrary(core, {});
-var _js_helper = dart.lazyImport(_js_helper);
-var _internal = dart.lazyImport(_internal);
-var collection = dart.lazyImport(collection);
-var _interceptors = dart.lazyImport(_interceptors);
-var convert = dart.lazyImport(convert);
-(function(exports, _js_helper, _internal, collection, _interceptors, convert) {
+dart.library('dart/core.js', null, /* Imports */[
+], /* Lazy imports */[
+  'dart/_js_helper.js',
+  'dart/_internal.js',
+  'dart/collection.js',
+  'dart/_interceptors.js',
+  'dart/convert.js'
+], function(exports, _js_helper, _internal, collection, _interceptors, convert) {
   'use strict';
   class Object {
     constructor() {
       let name = this.constructor.name;
       let init = this[name];
       let result = void 0;
       if (init)
         result = init.apply(this, arguments);
       return result === void 0 ? this : result;
     }
@@ skipping 3337 matching lines @@
   exports.Sink = Sink;
   exports.StackTrace = StackTrace;
   exports.Stopwatch = Stopwatch;
   exports.String = String;
   exports.RuneIterator = RuneIterator;
   exports.StringBuffer = StringBuffer;
   exports.StringSink = StringSink;
   exports.Symbol = Symbol;
   exports.Type = Type;
   exports.Uri = Uri;
-})(core, _js_helper, _internal, collection, _interceptors, convert);
+});