Check for duplicate library names

lib/runtime/dart/_internal.js

-var _internal = dart.defineLibrary(_internal, {});
-var core = dart.import(core);
-var collection = dart.import(collection);
-var math = dart.lazyImport(math);
-var _interceptors = dart.lazyImport(_interceptors);
-var _js_primitives = dart.lazyImport(_js_primitives);
-(function(exports, core, collection, math, _interceptors, _js_primitives) {
+dart.library('dart/_internal', null, /* Imports */[
+  'dart/core',
+  'dart/collection'
+], /* Lazy imports */[
+  'dart/math',
+  'dart/_interceptors',
+  'dart/_js_primitives'
+], function(exports, core, collection, math, _interceptors, _js_primitives) {
   'use strict';
   class EfficientLength extends core.Object {}
   let ListIterable$ = dart.generic(function(E) {
     class ListIterable extends collection.IterableBase$(E) {
       ListIterable() {
         super.IterableBase();
       }
       get iterator() {
         return new (ListIterator$(E))(this);
       }
@@ skipping 2402 matching lines @@
   exports.ReversedListIterable$ = ReversedListIterable$;
   exports.ReversedListIterable = ReversedListIterable;
   exports.UnmodifiableListError = UnmodifiableListError;
   exports.NonGrowableListError = NonGrowableListError;
   exports.makeListFixedLength = makeListFixedLength;
   exports.Lists = Lists;
   exports.printToConsole = printToConsole;
   exports.Sort = Sort;
   exports.Symbol = Symbol;
   exports.POWERS_OF_TEN = POWERS_OF_TEN;
-})(_internal, core, collection, math, _interceptors, _js_primitives);
+});