Fix off-by-one error in AstTyper, part 2.

test/mjsunit/regress/regress-param-local-type.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 24 matching lines @@
   var n = 0;
   var i = 1;
   n = i + a;
 }
 
 f(1);
 f(1);
 %OptimizeFunctionOnNextCall(f);
 f(1);
 assertOptimized(f);
+
+
+function g() {  // 0th parameter (receiver) is tagged.
+  var s = '';   // First local has string type.
+  var n = 0;
+  var i = 1;
+  n = i + this;
+}
+
+g.call(1);
+g.call(1);
+%OptimizeFunctionOnNextCall(g);
+g.call(1);
+assertOptimized(g);