Create pre-frozen change records for Object.observe

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 12413123c09c2a922da3f76a7fbe3679a3dd0609..52dd1564ccddde620f7220d03e232eaede1e40d4 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2217,6 +2217,10 @@ class JSObject: public JSReceiver {
                                   const char* type,
                                   Handle<String> name,
                                   Handle<Object> old_value);
+  static void EnqueueChangeRecord(Handle<JSObject> object,
+                                  Handle<String> type,
+                                  Handle<String> name,
+                                  Handle<Object> old_value);
 
   // Deliver change records to observers. May cause GC.
   static void DeliverChangeRecords(Isolate* isolate);
@@ -8324,6 +8328,26 @@ class JSRegExpResult: public JSArray {
 };
 
 
+// JSChangeRecords are JSObjects with a particular initial map
+// that includes in-object properties and non-extensibility.
+class JSChangeRecord: public JSObject {
+ public:
+  // Offsets of object fields.
+  static const int kTypeOffset = JSObject::kHeaderSize;
+  static const int kObjectOffset = kTypeOffset + kPointerSize;
+  static const int kNameOffset = kObjectOffset + kPointerSize;
+  static const int kOldValueOffset = kNameOffset + kPointerSize;
+  static const int kSize = kOldValueOffset + kPointerSize;
+  // Indices of in-object properties.
+  static const int kTypeIndex = 0;
+  static const int kObjectIndex = 1;
+  static const int kNameIndex = 2;
+  static const int kOldValueIndex = 3;
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(JSChangeRecord);
+};
+
+
 // An accessor must have a getter, but can have no setter.
 //
 // When setting a property, V8 searches accessors in prototypes.