Fixing compiler warning on gcc 4.6.1.

src/objects-inl.h

 // Copyright 2011 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 2280 matching lines @@
 }
 
 
 void ConsString::set_second(String* value, WriteBarrierMode mode) {
   WRITE_FIELD(this, kSecondOffset, value);
   CONDITIONAL_WRITE_BARRIER(GetHeap(), this, kSecondOffset, value, mode);
 }
 
 
 void ExternalString::clear_data_cache() {
-  WRITE_INTPTR_FIELD(this, kResourceDataOffset, NULL);
+  WRITE_INTPTR_FIELD(this, kResourceDataOffset, 0);
 }
 
 
 const ExternalAsciiString::Resource* ExternalAsciiString::resource() {
   return *reinterpret_cast<Resource**>(FIELD_ADDR(this, kResourceOffset));
 }
 
 
 void ExternalAsciiString::set_resource(
     const ExternalAsciiString::Resource* resource) {
@@ skipping 2357 matching lines @@
 #undef WRITE_INT_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_