Do not export natives to runtime via js builtins object.

src/collection.js

Index: src/collection.js
diff --git a/src/collection.js b/src/collection.js
index f0bc42392d9b117e3204e0135d2bb621ff248eb3..6d43384e1cecf440de2abc3067cab0a51528ae9c 100644
--- a/src/collection.js
+++ b/src/collection.js
@@ -4,14 +4,6 @@
 
 var $getHash;
 var $getExistingHash;
-var $mapSet;
-var $mapHas;
-var $mapDelete;
-var $setAdd;
-var $setHas;
-var $setDelete;
-var $mapFromArray;
-var $setFromArray;
 
 (function(global, utils) {
 "use strict";
@@ -487,15 +479,8 @@ utils.InstallFunctions(GlobalMap.prototype, DONT_ENUM, [
 // Expose to the global scope.
 $getHash = GetHash;
 $getExistingHash = GetExistingHash;
-$mapGet = MapGet;
-$mapSet = MapSet;
-$mapHas = MapHas;
-$mapDelete = MapDelete;
-$setAdd = SetAdd;
-$setHas = SetHas;
-$setDelete = SetDelete;
-
-$mapFromArray = function(array) {
+
+function MapFromArray(array) {
   var map = new GlobalMap;
   var length = array.length;
   for (var i = 0; i < length; i += 2) {
@@ -506,7 +491,7 @@ $mapFromArray = function(array) {
   return map;
 };
 
-$setFromArray = function(array) {
+function SetFromArray(array) {
   var set = new GlobalSet;
   var length = array.length;
   for (var i = 0; i < length; ++i) {
@@ -515,4 +500,19 @@ $setFromArray = function(array) {
   return set;
 };
 
+// -----------------------------------------------------------------------
+// Exports
+
+utils.ExportToRuntime(function(to) {
+  to.MapGet = MapGet;
+  to.MapSet = MapSet;
+  to.MapHas = MapHas;
+  to.MapDelete = MapDelete;
+  to.SetAdd = SetAdd;
+  to.SetHas = SetHas;
+  to.SetDelete = SetDelete;
+  to.MapFromArray = MapFromArray;
+  to.SetFromArray = SetFromArray;
+});
+
 })