Keep representations while overwriting transitions.

test/mjsunit/track-fields.js

 // Copyright 2013 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 288 matching lines @@
 var ftest4 = test_f(10);
 assertFalse(%HaveSameMap(ftest1, ftest3));
 assertTrue(%HaveSameMap(ftest3, ftest4));
 ftest2.func = is_writable;
 test_fic(ftest1);
 test_fic(ftest2);
 test_fic(ftest3);
 test_fic(ftest4);
 assertTrue(%HaveSameMap(ftest1, ftest3));
 assertTrue(%HaveSameMap(ftest3, ftest4));
+
+// Test representations and transition conversions.
+function read_first_double(o) {
+  return o.first_double;
+}
+var df1 = {};
+df1.first_double=1.6;
+read_first_double(df1);
+read_first_double(df1);
+function some_function1() { return 10; }
+var df2 = {};
+df2.first_double = 1.7;
+df2.second_function = some_function1;
+function some_function2() { return 20; }
+var df3 = {};
+df3.first_double = 1.7;
+df3.second_function = some_function2;
+df1.first_double = 10;
+read_first_double(df1);