Add a weak property type to the virtual machine.

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 4ef02b7bfdc8bd81a66dd9d7dd8f34f1136cbe8a..be8a4e68f1216b7c454388fced77e37b88e569dc 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -716,6 +716,11 @@ RawError* Object::Init(Isolate* isolate) {
   RegisterClass(cls, "JSSyntaxRegExp", impl_script, core_impl_lib);
   pending_classes.Add(cls, Heap::kOld);
 
+  cls = Class::New<WeakProperty>();
+  object_store->set_weak_property_class(cls);
+  RegisterClass(cls, "WeakProperty", impl_script, core_impl_lib);
+  pending_classes.Add(cls, Heap::kOld);
+
   // Initialize the base interfaces used by the core VM classes.
   const Script& script = Script::Handle(Bootstrap::LoadScript());
 
@@ -1060,6 +1065,9 @@ void Object::InitFromSnapshot(Isolate* isolate) {
   cls = Class::New<JSRegExp>();
   object_store->set_jsregexp_class(cls);
 
+  cls = Class::New<WeakProperty>();
+  object_store->set_weak_property_class(cls);
+
   // Allocate pre-initialized values.
   Bool& bool_value = Bool::Handle();
   bool_value = Bool::New(true);
@@ -1827,6 +1835,9 @@ RawClass* Class::GetClass(ObjectKind kind) {
     case kJSRegExp:
       ASSERT(object_store->jsregexp_class() != Class::null());
       return object_store->jsregexp_class();
+    case kWeakProperty:
+      ASSERT(object_store->weak_property_class() != Class::null());
+      return object_store->weak_property_class();
     case kClosure:
       return Class::New<Closure>();
     case kInstance:
@@ -11193,4 +11204,24 @@ const char* JSRegExp::ToCString() const {
   return chars;
 }
 
+
+RawWeakProperty* WeakProperty::New(Heap::Space space) {
+  ASSERT(Isolate::Current()->object_store()->weak_property_class()
+         != Class::null());
+  WeakProperty& result = WeakProperty::Handle();
+  {
+    RawObject* raw = Object::Allocate(WeakProperty::kInstanceKind,
+                                      WeakProperty::InstanceSize(),
+                                      space);

[turnidge, 2012/08/09 18:34:34]

Just to double-check, does Object::Allocate set (key/value/next) to null?

[cshapiro, 2012/08/14 04:58:18]

Yes, it should.

+    NoGCScope no_gc;
+    result ^= raw;
+  }
+  return result.raw();
+}
+
+
+const char* WeakProperty::ToCString() const {
+  return "WeakProperty";

[turnidge, 2012/08/09 18:34:34]

A thought: you could make the ToCString have some info about the key and the
value.  Your call.

[cshapiro, 2012/08/14 04:58:18]

Yes, I could although I cannot think of anything now.  Let me know if I am
missing something obvious.

+}
+
 }  // namespace dart