ES6: Adding support for size to Set and Map

src/v8natives.js

Index: src/v8natives.js
diff --git a/src/v8natives.js b/src/v8natives.js
index e2e642941e9e95fc882b2b024d2ff69812bdd631..32e673c5f38e58573c44f820602b8050831eaad3 100644
--- a/src/v8natives.js
+++ b/src/v8natives.js
@@ -60,6 +60,16 @@ function InstallFunctions(object, attributes, functions) {
   %ToFastProperties(object);
 }
 
+
+// Helper function to install a getter only property.
+function InstallGetter(object, name, getter) {
+  %FunctionSetName(getter, name);
+  %FunctionRemovePrototype(getter);
+  %DefineOrRedefineAccessorProperty(object, name, getter, null, DONT_ENUM);
+  %SetNativeFlag(getter);
+}
+
+
 // Prevents changes to the prototype of a built-infunction.
 // The "prototype" property of the function object is made non-configurable,
 // and the prototype object is made non-extensible. The latter prevents