Implement implicit instance checks for API accessors.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 076368830a934e3fa16080923443d16f75e1c225..d5b397c5cffc05f810a71b1dbbb99f2b629cf661 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8086,6 +8086,7 @@ class AccessorInfo: public Struct {
   DECL_ACCESSORS(data, Object)
   DECL_ACCESSORS(name, Object)
   DECL_ACCESSORS(flag, Smi)
+  DECL_ACCESSORS(expected_receiver_type, Object)
 
   inline bool all_can_read();
   inline void set_all_can_read(bool value);
@@ -8099,6 +8100,9 @@ class AccessorInfo: public Struct {
   inline PropertyAttributes property_attributes();
   inline void set_property_attributes(PropertyAttributes attributes);
 
+  // Checks whether the given receiver is compatible with this accessor.
+  inline bool IsCompatibleReceiver(Object* receiver);
+
   static inline AccessorInfo* cast(Object* obj);
 
 #ifdef OBJECT_PRINT
@@ -8116,7 +8120,8 @@ class AccessorInfo: public Struct {
   static const int kDataOffset = kSetterOffset + kPointerSize;
   static const int kNameOffset = kDataOffset + kPointerSize;
   static const int kFlagOffset = kNameOffset + kPointerSize;
-  static const int kSize = kFlagOffset + kPointerSize;
+  static const int kExpectedReceiverTypeOffset = kFlagOffset + kPointerSize;
+  static const int kSize = kExpectedReceiverTypeOffset + kPointerSize;
 
  private:
   // Bit positions in flag.