Trying to move derived get trap from builtins to global context.

src/proxy.js

Index: src/proxy.js
diff --git a/src/proxy.js b/src/proxy.js
index 01d48b485ac193a19c6cc681b4e88a1533f56945..c11852b0f89f5ca84b698c43ef04ff8d3b00b88a 100644
--- a/src/proxy.js
+++ b/src/proxy.js
@@ -63,3 +63,21 @@ $Proxy.create = function(handler, proto) {
   if (!IS_SPEC_OBJECT(proto)) proto = $Object.prototype
   return %CreateJSProxy(handler, proto)
 }
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// Builtins
+////////////////////////////////////////////////////////////////////////////////
+
+function DerivedGetTrap(receiver, name) {
+  var desc = this.getPropertyDescriptor(name)
+  if (IS_UNDEFINED(desc)) { return desc; }
+  if ('value' in desc) {
+    return desc.value
+  } else {
+    if (IS_UNDEFINED(desc.get)) { return desc.get; }
+    return desc.get.call(receiver)  // The proposal says so...
+  }
+}