Stack allocate lexical locals + hoist stack slots

test/mjsunit/es6/debug-function-scopes.js

 // Copyright 2012 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 89 matching lines @@
         return function() {
           return l0 + v1 + v3 + l2 + l3 + v6;
         };
       }
     }
   }
 })();
 
 var mirror = Debug.MakeMirror(f2);
 
-assertEquals(6, mirror.scopeCount());
+assertEquals(5, mirror.scopeCount());
 
-// Implementation artifact: l4 isn't used in closure, but still it is saved.
-CheckScope(mirror.scope(0), { l4: 11 }, ScopeType.Block);
-
-CheckScope(mirror.scope(1), { l3: 9 }, ScopeType.Block);
-CheckScope(mirror.scope(2), { l1: 6, l2: 7 }, ScopeType.Block);
-CheckScope(mirror.scope(3), { v1:3, l0: 0, v3: 5, v6: 11 }, ScopeType.Closure);
-CheckScope(mirror.scope(4), { top_level_let: 255 }, ScopeType.Script);
-CheckScope(mirror.scope(5), {}, ScopeType.Global);
+CheckScope(mirror.scope(0), { l3: 9 }, ScopeType.Block);
+CheckScope(mirror.scope(1), { l2: 7 }, ScopeType.Block);
+CheckScope(mirror.scope(2), { v1:3, l0: 0, v3: 5, v6: 11 }, ScopeType.Closure);
+CheckScope(mirror.scope(3), { top_level_let: 255 }, ScopeType.Script);
+CheckScope(mirror.scope(4), {}, ScopeType.Global);