Add Map::weak_cell_cache internal link to heap snapshot.

test/cctest/test-heap-profiler.cc

 // Copyright 2011 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 670 matching lines @@
       ++entries;
     }
   }
   CHECK_EQ(2, entries);
   const v8::HeapGraphNode* map_s =
       GetProperty(map, v8::HeapGraphEdge::kProperty, "str");
   CHECK(map_s);
   CHECK_EQ(s->GetId(), map_s->GetId());
 }
 
+TEST(HeapSnapshotMap) {
+  LocalContext env;
+  v8::HandleScope scope(env->GetIsolate());
+  v8::HeapProfiler* heap_profiler = env->GetIsolate()->GetHeapProfiler();
+
+  CompileRun(
+      "function Z() { this.foo = {}; }\n"
+      "z = new Z();\n");
+  const v8::HeapSnapshot* snapshot = heap_profiler->TakeHeapSnapshot();
+  CHECK(ValidateSnapshot(snapshot));
+  const v8::HeapGraphNode* global = GetGlobalObject(snapshot);
+  const v8::HeapGraphNode* z =
+      GetProperty(global, v8::HeapGraphEdge::kProperty, "z");
+  CHECK(z);
+  const v8::HeapGraphNode* map =
+      GetProperty(z, v8::HeapGraphEdge::kInternal, "map");
+  CHECK(map);
+  CHECK(GetProperty(map, v8::HeapGraphEdge::kInternal, "map"));
+  CHECK(GetProperty(map, v8::HeapGraphEdge::kInternal, "prototype"));
+  CHECK(GetProperty(map, v8::HeapGraphEdge::kInternal, "back_pointer"));
+  CHECK(GetProperty(map, v8::HeapGraphEdge::kInternal, "descriptors"));
+  CHECK(GetProperty(map, v8::HeapGraphEdge::kInternal, "weak_cell_cache"));
+}
 
 TEST(HeapSnapshotInternalReferences) {
   v8::Isolate* isolate = CcTest::isolate();
   v8::HandleScope scope(isolate);
   v8::Local<v8::ObjectTemplate> global_template =
       v8::ObjectTemplate::New(isolate);
   global_template->SetInternalFieldCount(2);
   LocalContext env(NULL, global_template);
   v8::Local<v8::Object> global_proxy = env->Global();
   v8::Local<v8::Object> global = global_proxy->GetPrototype().As<v8::Object>();
@@ skipping 2376 matching lines @@
       "      a[i] = i;\n"
       "  for (var i = 0; i < 3; ++i)\n"
       "      a.shift();\n"
       "}\n");
 
   CcTest::heap()->CollectGarbage(v8::internal::NEW_SPACE);
   // Should not crash.
 
   heap_profiler->StopSamplingHeapProfiler();
 }