Add API for access checks on observed objects

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index f1fa27accdef209ed0e0653f6bd20b331a3b24e9..c526c161b1471d7eee0b0aba9b313452f59a1a73 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8349,6 +8349,7 @@ class AccessCheckInfo: public Struct {
  public:
   DECL_ACCESSORS(named_callback, Object)
   DECL_ACCESSORS(indexed_callback, Object)
+  DECL_ACCESSORS(observe_callback, Object)
   DECL_ACCESSORS(data, Object)
 
   static inline AccessCheckInfo* cast(Object* obj);
@@ -8359,7 +8360,9 @@ class AccessCheckInfo: public Struct {
 
   static const int kNamedCallbackOffset   = HeapObject::kHeaderSize;
   static const int kIndexedCallbackOffset = kNamedCallbackOffset + kPointerSize;
-  static const int kDataOffset = kIndexedCallbackOffset + kPointerSize;
+  static const int kObserveCallbackOffset =
+      kIndexedCallbackOffset + kPointerSize;
+  static const int kDataOffset = kObserveCallbackOffset + kPointerSize;
   static const int kSize = kDataOffset + kPointerSize;
 
  private: