Add another check in profiler's stack iterator to ensure stability.

src/frames-inl.h

 // Copyright 2006-2008 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 153 matching lines @@
 }
 
 
 inline bool JavaScriptFrame::has_adapted_arguments() const {
   return IsArgumentsAdaptorFrame(caller_fp());
 }
 
 
 inline bool JavaScriptFrame::is_at_function() const {
   Object* result = function_slot_object();
+  // Verify that frame points at correct JS function object.
+  // We are verifying that function object address and
+  // the underlying map object address are valid, and that
+  // function is really a function.
   return Heap::Contains(reinterpret_cast<Address>(result)) &&
+      result->IsHeapObject() &&
+      Heap::Contains(HeapObject::cast(result)->map()) &&
       result->IsJSFunction();
 }
 
 
 inline Object* JavaScriptFrame::function() const {
   Object* result = function_slot_object();
   ASSERT(result->IsJSFunction());
   return result;
 }
 
@@ skipping 39 matching lines @@
 template<typename Iterator>
 void JavaScriptFrameIteratorTemp<Iterator>::Reset() {
   iterator_.Reset();
   if (!done()) Advance();
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_FRAMES_INL_H_