fixes #157, renaming local library identifiers if needed.

lib/runtime/dart/collection.js

Index: lib/runtime/dart/collection.js
diff --git a/lib/runtime/dart/collection.js b/lib/runtime/dart/collection.js
index 3ad62e121ad676df978ed856fd2ab38d33f35659..41cc67edb9b37b4c282f7036b64de6aeab09b19b 100644
--- a/lib/runtime/dart/collection.js
+++ b/lib/runtime/dart/collection.js
@@ -1,5 +1,5 @@
-var collection;
-(function(exports) {
+var collection, _internal, core, _js_helper, math;
+(function(exports, _internal, core, _js_helper, math) {
   'use strict';
   let _source = Symbol('_source');
   let UnmodifiableListView$ = dart.generic(function(E) {
@@ -5198,4 +5198,4 @@ var collection;
   exports.LinkedHashSetCell = LinkedHashSetCell;
   exports.LinkedHashSetIterator$ = LinkedHashSetIterator$;
   exports.LinkedHashSetIterator = LinkedHashSetIterator;
-})(collection || (collection = {}));
+})(collection || (collection = {}), _internal || (_internal = {}), core, _js_helper || (_js_helper = {}), math || (math = {}));