[es6] Further fixing of tail Calls.

test/mjsunit/strict-mode.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 1131 matching lines @@
 })();
 
 
 (function TestNonStrictFunctionCallerPillSimple() {
   function return_my_caller() {
     return return_my_caller.caller;
   }
 
   function strict() {
     "use strict";
-    return return_my_caller();
+    // Returning result via local variable to avoid tail call optimization.
+    var res = return_my_caller();
+    return res;
   }
   assertSame(null, strict());
 
   function non_strict() {
     return return_my_caller();
   }
   assertSame(non_strict(), non_strict);
 })();
 
 
 (function TestNonStrictFunctionCallerPill() {
   function strict(n) {
     "use strict";
-    return non_strict(n);
+    // Returning result via local variable to avoid tail call optimization.
+    var res = non_strict(n);
+    return res;
   }
 
   function recurse(n, then) {
     if (n > 0) {
       return recurse(n - 1, then);
     } else {
       return then();
     }
   }
 
   function non_strict(n) {
     return recurse(n, function() { return non_strict.caller; });
   }
 
   function test(n) {
     return recurse(n, function() { return strict(n); });
   }
 
   for (var i = 0; i < 10; i ++) {
     assertSame(null, test(i));
   }
 })();
 
 
 (function TestNonStrictFunctionCallerDescriptorPill() {
   function strict(n) {
     "use strict";
-    return non_strict(n);
+    // Returning result via local variable to avoid tail call optimization.
+    var res = non_strict(n);
+    return res;
   }
 
   function recurse(n, then) {
     if (n > 0) {
       return recurse(n - 1, then);
     } else {
       return then();
     }
   }
 
@@ skipping 11 matching lines @@
     assertSame(null, test(i));
   }
 })();
 
 
 (function TestStrictModeEval() {
   "use strict";
   eval("var eval_local = 10;");
   assertThrows(function() { return eval_local; }, ReferenceError);
 })();