Cleanup of mjsunit.js code and make assertEquals more strict.

test/mjsunit/const.js

 // Copyright 2008 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 32 matching lines @@
 }
 
 f();
 
 // Test that the value is read eventhough assignment is disallowed.
 // Spidermonkey does not do this, but it seems like the right thing to
 // do so that 'o++' is equivalent to 'o = o + 1'.
 var valueOfCount = 0;
 
 function g() {
-  const o = { valueOf: function() { valueOfCount++; return 42; } }
-  assertEquals(42, o);
+  const o = { valueOf: function() { valueOfCount++; return 42; } };
+  assertEquals(42, +o);
   assertEquals(1, valueOfCount);
   o++;
-  assertEquals(42, o);
+  assertEquals(42, +o);
   assertEquals(3, valueOfCount);
   ++o;
-  assertEquals(42, o);
+  assertEquals(42, +o);
   assertEquals(5, valueOfCount);
   o--;
-  assertEquals(42, o);
+  assertEquals(42, +o);
   assertEquals(7, valueOfCount);
   --o;
-  assertEquals(42, o);
+  assertEquals(42, +o);
   assertEquals(9, valueOfCount);
 }
 
 g();