Implemented Object.keys.

src/v8natives.js

Index: src/v8natives.js
diff --git a/src/v8natives.js b/src/v8natives.js
index be92347768a71867c546785641dff8b6718ceb60..b63ce5f1082519d0543dd276f301631e74e25af7 100644
--- a/src/v8natives.js
+++ b/src/v8natives.js
@@ -276,6 +276,13 @@ function ObjectLookupSetter(name) {
 }
 
 
+function ObjectKeys(obj) {
+  if (!IS_OBJECT(obj) || IS_NULL_OR_UNDEFINED(obj))
+    throw MakeTypeError('object_keys_non_object', [obj]);
+  return %LocalKeys(obj);
+}
+
+
 %SetCode($Object, function(x) {
   if (%_IsConstructCall()) {
     if (x == null) return this;
@@ -304,6 +311,9 @@ function SetupObject() {
     "__defineSetter__", ObjectDefineSetter,
     "__lookupSetter__", ObjectLookupSetter
   ));
+  InstallFunctions($Object, DONT_ENUM, $Array(
+    "keys", ObjectKeys
+  ));
 }
 
 SetupObject();