Add an API for enumerating persistent handles

test/cctest/test-api.cc

Index: test/cctest/test-api.cc
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index a8f340db2e4e89627fa1718cea71b7bf5ca73e88..78151881655a8e270f8f7226aaf51562f1d11ce6 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -5229,7 +5229,9 @@ THREADED_TEST(IndependentWeakHandle) {
 
   bool object_a_disposed = false;
   object_a.MakeWeak(&object_a_disposed, &DisposeAndSetFlag);
+  CHECK(!object_a.IsIndependent());
   object_a.MarkIndependent();
+  CHECK(object_a.IsIndependent());
   HEAP->PerformScavenge();
   CHECK(object_a_disposed);
 }
@@ -16177,6 +16179,43 @@ TEST(DontDeleteCellLoadICAPI) {
 }
 
 
+TEST(PersistentHandleVisitor) {
+  v8::HandleScope scope;
+  LocalContext context;
+  v8::Persistent<v8::Object> object =
+      v8::Persistent<v8::Object>::New(v8::Object::New());
+  CHECK_EQ(0, object.WrapperClassId());
+  object.SetWrapperClassId(42);
+  CHECK_EQ(42, object.WrapperClassId());
+
+  class Visitor : public v8::PersistentHandleVisitor {
+   public:
+    explicit Visitor(v8::Persistent<v8::Object> object)
+      : counter_(0), object_(object) { }
+
+    virtual void VisitPersistentHandle(Persistent<Value> value,
+                                       uint16_t class_id) {
+      if (class_id == 42) {
+        CHECK(value->IsObject());
+        v8::Persistent<v8::Object> visited =
+            v8::Persistent<v8::Object>::Cast(value);
+        CHECK_EQ(42, visited.WrapperClassId());
+        CHECK_EQ(object_, visited);
+        ++counter_;
+      }
+    }
+
+    int counter_;
+    v8::Persistent<v8::Object> object_;
+  } visitor(object);
+
+  v8::V8::VisitHandlesWithClassIds(&visitor);
+  CHECK_EQ(1, visitor.counter_);
+
+  object.Dispose();
+}
+
+
 TEST(RegExp) {
   v8::HandleScope scope;
   LocalContext context;