Reland "Fix memory leak caused by field type in descriptor array."

test/cctest/test-heap.cc

Index: test/cctest/test-heap.cc
diff --git a/test/cctest/test-heap.cc b/test/cctest/test-heap.cc
index cd012f6bfa91b942771008077c02715ef8535ea7..f5d71c37fccb0788df53f86d134f7b60ec94d64e 100644
--- a/test/cctest/test-heap.cc
+++ b/test/cctest/test-heap.cc
@@ -5062,6 +5062,40 @@ TEST(NumberStringCacheSize) {
 }
 
 
+TEST(Regress3877) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  Heap* heap = isolate->heap();
+  Factory* factory = isolate->factory();
+  HandleScope scope(isolate);
+  CompileRun("function cls() { this.x = 10; }");
+  Handle<WeakCell> weak_prototype;
+  {
+    HandleScope inner_scope(isolate);
+    v8::Local<v8::Value> result = CompileRun("cls.prototype");
+    Handle<JSObject> proto =
+        v8::Utils::OpenHandle(*v8::Handle<v8::Object>::Cast(result));
+    weak_prototype = inner_scope.CloseAndEscape(factory->NewWeakCell(proto));
+  }
+  CHECK(!weak_prototype->cleared());
+  CompileRun(
+      "var a = { };"
+      "a.x = new cls();"
+      "cls.prototype = null;");
+  for (int i = 0; i < 4; i++) {
+    heap->CollectAllGarbage(Heap::kNoGCFlags);
+  }
+  // The map of a.x keeps prototype alive
+  CHECK(!weak_prototype->cleared());
+  // Change the map of a.x and make the previous map garbage collectable.
+  CompileRun("a.x.__proto__ = {};");
+  for (int i = 0; i < 4; i++) {
+    heap->CollectAllGarbage(Heap::kNoGCFlags);
+  }
+  CHECK(weak_prototype->cleared());
+}
+
+
 void CheckMapRetainingFor(int n) {
   FLAG_retain_maps_for_n_gc = n;
   Isolate* isolate = CcTest::i_isolate();