fixes #157, renaming local library identifiers if needed.

lib/runtime/dart/collection.js

-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) {
     class UnmodifiableListView extends _internal.UnmodifiableListBase$(E) {
       UnmodifiableListView(source) {
         this[_source] = source;
       }
       get [core.$length]() {
         return this[_source][core.$length];
       }
@@ skipping 5178 matching lines @@
   exports.LinkedHashMapCell = LinkedHashMapCell;
   exports.LinkedHashMapKeyIterable$ = LinkedHashMapKeyIterable$;
   exports.LinkedHashMapKeyIterable = LinkedHashMapKeyIterable;
   exports.LinkedHashMapKeyIterator$ = LinkedHashMapKeyIterator$;
   exports.LinkedHashMapKeyIterator = LinkedHashMapKeyIterator;
   exports.HashSetIterator$ = HashSetIterator$;
   exports.HashSetIterator = HashSetIterator;
   exports.LinkedHashSetCell = LinkedHashSetCell;
   exports.LinkedHashSetIterator$ = LinkedHashSetIterator$;
   exports.LinkedHashSetIterator = LinkedHashSetIterator;
-})(collection || (collection = {}));
+})(collection || (collection = {}), _internal || (_internal = {}), core, _js_helper || (_js_helper = {}), math || (math = {}));