Reland "Enable Object.observe by default" again

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 1985 matching lines @@
   CcTest::heap()->CollectGarbage(OLD_POINTER_SPACE);
 }
 
 
 TEST(PrototypeTransitionClearing) {
   CcTest::InitializeVM();
   Isolate* isolate = CcTest::i_isolate();
   Factory* factory = isolate->factory();
   v8::HandleScope scope(CcTest::isolate());
 
+  CompileRun("var base = {};");
+  Handle<JSObject> baseObject =
+      v8::Utils::OpenHandle(
+          *v8::Handle<v8::Object>::Cast(
+              CcTest::global()->Get(v8_str("base"))));
+  int initialTransitions = baseObject->map()->NumberOfProtoTransitions();
+
   CompileRun(
-      "var base = {};"
       "var live = [];"
       "for (var i = 0; i < 10; i++) {"
       "  var object = {};"
       "  var prototype = {};"
       "  object.__proto__ = prototype;"
       "  if (i >= 3) live.push(object, prototype);"
       "}");
 
-  Handle<JSObject> baseObject =
-      v8::Utils::OpenHandle(
-          *v8::Handle<v8::Object>::Cast(
-              CcTest::global()->Get(v8_str("base"))));
-
   // Verify that only dead prototype transitions are cleared.
-  CHECK_EQ(10, baseObject->map()->NumberOfProtoTransitions());
+  CHECK_EQ(initialTransitions + 10,
+      baseObject->map()->NumberOfProtoTransitions());
   CcTest::heap()->CollectAllGarbage(Heap::kAbortIncrementalMarkingMask);
   const int transitions = 10 - 3;
-  CHECK_EQ(transitions, baseObject->map()->NumberOfProtoTransitions());
+  CHECK_EQ(initialTransitions + transitions,
+      baseObject->map()->NumberOfProtoTransitions());
 
   // Verify that prototype transitions array was compacted.
   FixedArray* trans = baseObject->map()->GetPrototypeTransitions();
-  for (int i = 0; i < transitions; i++) {
+  for (int i = initialTransitions; i < initialTransitions + transitions; i++) {
     int j = Map::kProtoTransitionHeaderSize +
         i * Map::kProtoTransitionElementsPerEntry;
     CHECK(trans->get(j + Map::kProtoTransitionMapOffset)->IsMap());
     Object* proto = trans->get(j + Map::kProtoTransitionPrototypeOffset);
-    CHECK(proto->IsTheHole() || proto->IsJSObject());
+    CHECK(proto->IsJSObject());
   }
 
   // Make sure next prototype is placed on an old-space evacuation candidate.
   Handle<JSObject> prototype;
   PagedSpace* space = CcTest::heap()->old_pointer_space();
   {
     AlwaysAllocateScope always_allocate;
     SimulateFullSpace(space);
     prototype = factory->NewJSArray(32 * KB, FAST_HOLEY_ELEMENTS, TENURED);
   }
@@ skipping 1685 matching lines @@
   v8::Handle<v8::Object> global = CcTest::global();
     v8::Handle<v8::Function> g =
         v8::Handle<v8::Function>::Cast(global->Get(v8_str("crash")));
   v8::Handle<v8::Value> args1[] = { v8_num(1) };
   heap->DisableInlineAllocation();
   heap->set_allocation_timeout(1);
   g->Call(global, 1, args1);
   heap->CollectAllGarbage(Heap::kAbortIncrementalMarkingMask);
 }
 #endif