Push version 2.5.7 to trunk....

src/handles.cc

 // Copyright 2009 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 481 matching lines @@
     Handle<FixedArray> empty = Factory::NewFixedArray(0);
     script->set_line_ends(*empty);
     ASSERT(script->line_ends()->IsFixedArray());
     return;
   }
 
   Handle<String> src(String::cast(script->source()));
 
   Handle<FixedArray> array = CalculateLineEnds(src, true);
 
+  if (*array != Heap::empty_fixed_array()) {
+    array->set_map(Heap::fixed_cow_array_map());
+  }
+
   script->set_line_ends(*array);
   ASSERT(script->line_ends()->IsFixedArray());
 }
 
 
 Handle<FixedArray> CalculateLineEnds(Handle<String> src,
                                      bool with_imaginary_last_new_line) {
   const int src_len = src->length();
   Handle<String> new_line = Factory::NewStringFromAscii(CStrVector("\n"));
 
@@ skipping 352 matching lines @@
 
 OptimizedObjectForAddingMultipleProperties::
 ~OptimizedObjectForAddingMultipleProperties() {
   // Reoptimize the object to allow fast property access.
   if (has_been_transformed_) {
     TransformToFastProperties(object_, unused_property_fields_);
   }
 }
 
 } }  // namespace v8::internal