Dramatically speed up detailed heap snapshot generation.

src/objects.h

 // Copyright 2010 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 1569 matching lines @@
   bool HasRealNamedCallbackProperty(String* key);
 
   // Initializes the array to a certain length
   MUST_USE_RESULT MaybeObject* SetElementsLength(Object* length);
 
   // Get the header size for a JSObject.  Used to compute the index of
   // internal fields as well as the number of internal fields.
   inline int GetHeaderSize();
 
   inline int GetInternalFieldCount();
+  inline int GetInternalFieldOffset(int index);
   inline Object* GetInternalField(int index);
   inline void SetInternalField(int index, Object* value);
 
   // Lookup a property.  If found, the result is valid and has
   // detailed information.
   void LocalLookup(String* name, LookupResult* result);
   void Lookup(String* name, LookupResult* result);
 
   // The following lookup functions skip interceptors.
   void LocalLookupRealNamedProperty(String* name, LookupResult* result);
@@ skipping 97 matching lines @@
   // Transform slow named properties to fast variants.
   // Returns failure if allocation failed.
   MUST_USE_RESULT MaybeObject* TransformToFastProperties(
       int unused_property_fields);
 
   // Access fast-case object properties at index.
   inline Object* FastPropertyAt(int index);
   inline Object* FastPropertyAtPut(int index, Object* value);
 
   // Access to in object properties.
+  inline int GetInObjectPropertyOffset(int index);
   inline Object* InObjectPropertyAt(int index);
   inline Object* InObjectPropertyAtPut(int index,
                                        Object* value,
                                        WriteBarrierMode mode
                                        = UPDATE_WRITE_BARRIER);
 
   // initializes the body after properties slot, properties slot is
   // initialized by set_properties
   // Note: this call does not update write barrier, it is caller's
   // reponsibility to ensure that *v* can be collected without WB here.
@@ skipping 4867 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_