Object.observe: Make array length and other magic data properties work correctly.

src/property.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 292 matching lines @@
   bool IsFound() { return lookup_type_ != NOT_FOUND; }
   bool IsTransition() { return lookup_type_ == TRANSITION_TYPE; }
   bool IsHandler() { return lookup_type_ == HANDLER_TYPE; }
   bool IsInterceptor() { return lookup_type_ == INTERCEPTOR_TYPE; }
 
   // Is the result is a property excluding transitions and the null descriptor?
   bool IsProperty() {
     return IsFound() && !IsTransition();
   }
 
+  bool IsDataProperty() {
+    switch (type()) {
+      case FIELD:
+      case NORMAL:
+      case CONSTANT_FUNCTION:
+        return true;
+      case CALLBACKS:
+        return GetCallbackObject()->IsForeign();

[Michael Starzinger, 2012/12/12 15:34:05]

I think AccessorInfo callbacks should also return true here, they also look like
data properties to JavaScript.

[rossberg, 2012/12/12 15:41:10]

Done.

+      default:

[Michael Starzinger, 2012/12/12 15:34:05]

I think Sven has to say something about this default case.

[rossberg, 2012/12/12 15:41:10]

Unfolded default (also in GetLazyValue below).

+        return false;
+    }
+  }
+
   bool IsCacheable() { return cacheable_; }
   void DisallowCaching() { cacheable_ = false; }
 
   Object* GetLazyValue() {
     switch (type()) {
       case FIELD:
         return holder()->FastPropertyAt(GetFieldIndex().field_index());
       case NORMAL: {
         Object* value;
         value = holder()->property_dictionary()->ValueAt(GetDictionaryEntry());
@@ skipping 124 matching lines @@
   JSReceiver* holder_;
   int number_;
   bool cacheable_;
   PropertyDetails details_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_PROPERTY_H_