Use import/export for more functions (instead of js builtins object).

src/js/arraybuffer.js

Index: src/js/arraybuffer.js
diff --git a/src/js/arraybuffer.js b/src/js/arraybuffer.js
index 2c1e9bd263c28a04a91f64a67dac2826e1758ab8..fb803caa5aace679c621158f2ce0f44bd55216d4 100644
--- a/src/js/arraybuffer.js
+++ b/src/js/arraybuffer.js
@@ -15,18 +15,20 @@ var GlobalArrayBuffer = global.ArrayBuffer;
 var GlobalObject = global.Object;
 var MathMax;
 var MathMin;
+var ToPositiveInteger;
 var toStringTagSymbol = utils.ImportNow("to_string_tag_symbol");
 
 utils.Import(function(from) {
   MathMax = from.MathMax;
   MathMin = from.MathMin;
+  ToPositiveInteger = from.ToPositiveInteger;
 });
 
 // -------------------------------------------------------------------
 
 function ArrayBufferConstructor(length) { // length = 1
   if (%_IsConstructCall()) {
-    var byteLength = $toPositiveInteger(length, kInvalidArrayBufferLength);
+    var byteLength = ToPositiveInteger(length, kInvalidArrayBufferLength);
     %ArrayBufferInitialize(this, byteLength, kNotShared);
   } else {
     throw MakeTypeError(kConstructorNotFunction, "ArrayBuffer");