Reland and fix "Fix LoadFieldByIndex to take mutable heap-numbers into account.""

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 9a6b26aaf11a9afd280ccd0bfca53a0c1e54cad5..78d2b8a038feb2fda955af5b39a24dd2d74ad1ea 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -5641,6 +5641,15 @@ Handle<JSObject> JSObject::Copy(Handle<JSObject> object) {
 }
 
 
+Handle<Object> JSObject::FastPropertyAt(Handle<JSObject> object,
+                                        Representation representation,
+                                        int index) {
+  Isolate* isolate = object->GetIsolate();
+  CALL_HEAP_FUNCTION(isolate,
+                     object->FastPropertyAt(representation, index), Object);
+}
+
+
 template<class ContextObject>
 class JSObjectWalkVisitor {
  public: