Fix PathTracer.

test/cctest/test-heap.cc

 // 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 4244 matching lines @@
       "array;");
 
   Handle<JSObject> o =
       v8::Utils::OpenHandle(*v8::Handle<v8::Object>::Cast(result));
   CHECK(heap->InOldPointerSpace(o->elements()));
   CHECK(heap->InOldPointerSpace(*o));
   Page* page = Page::FromAddress(o->elements()->address());
   CHECK(page->WasSwept() ||
         Marking::IsBlack(Marking::MarkBitFrom(o->elements())));
 }
+
+
+#ifdef DEBUG
+TEST(PathTracer) {
+  CcTest::InitializeVM();
+  v8::HandleScope scope(CcTest::isolate());
+
+  v8::Local<v8::Value> result = CompileRun("'abc'");
+  Handle<Object> o = v8::Utils::OpenHandle(*result);
+  CcTest::i_isolate()->heap()->TracePathToObject(*o);
+}
+#endif  // DEBUG