Revert of [turbofan] Set proper representation for initial arguments length.

test/mjsunit/arguments.js

 // 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 253 matching lines @@
   assertEquals(undefined, args[1]);
   assertEquals(key, args[key]);
   assertEquals(2, args.length);
 
   delete args[key];
   assertEquals(undefined, args[0]);
   assertEquals(undefined, args[1]);
   assertEquals(undefined, args[key]);
   assertEquals(2, args.length);
 })();
+
+(function testSloppyArgumentsLengthMapChange() {
+  function f(a) { return arguments };
+  let args1 = f(1);
+  let args2 = f(1,2);
+  assertTrue(%HaveSameMap(args1, args2));
+  // Changing the length type doesn't causes a map transition.
+  args2.length = 12;
+  assertTrue(%HaveSameMap(args1, args2));
+  args2.length = 12.0;
+  assertTrue(%HaveSameMap(args1, args2));
+  args2.length = "aa"
+  assertTrue(%HaveSameMap(args1, args2));
+})();