[builtins] Support SameValue and SameValueZero via runtime functions.

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index 677cfdd8aa9d90f6cc2864cda4ad15a18cfcef0f..2c00330584330b696ebf25a736a808a0fe483b62 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -1814,6 +1814,16 @@ BUILTIN(ObjectGetOwnPropertySymbols) {
 }
 
 
+// ES#sec-object.is Object.is ( value1, value2 )
+BUILTIN(ObjectIs) {
+  SealHandleScope shs(isolate);
+  DCHECK_EQ(3, args.length());
+  Handle<Object> value1 = args.at<Object>(1);
+  Handle<Object> value2 = args.at<Object>(2);
+  return isolate->heap()->ToBoolean(value1->SameValue(*value2));
+}
+
+
 // ES6 section 19.1.2.11 Object.isExtensible ( O )
 BUILTIN(ObjectIsExtensible) {
   HandleScope scope(isolate);