Add more checks for native callback results.

src/objects.h

 // 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 952 matching lines @@
 
   // Returns true if this is a JSValue containing a string and the index is
   // < the length of the string.  Used to implement [] on strings.
   inline bool IsStringObjectWithCharacterAt(uint32_t index);
 
 #ifdef DEBUG
   // Verify a pointer is a valid object pointer.
   static void VerifyPointer(Object* p);
 #endif
 
+  inline void VerifyApiCallResultType();
+
   // Prints this object without details.
   inline void ShortPrint() {
     ShortPrint(stdout);
   }
   void ShortPrint(FILE* out);
 
   // Prints this object without details to a message accumulator.
   void ShortPrint(StringStream* accumulator);
 
   // Casting: This cast is only needed to satisfy macros in objects-inl.h.
@@ skipping 7967 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_