Introduce with scope and rework variable resolution.

src/variables.h

 // 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 164 matching lines @@
   }
 
  private:
   Scope* scope_;
   Handle<String> name_;
   Mode mode_;
   Kind kind_;
   Location location_;
   int index_;
 
+  // If this field is set, this variable references the stored locally bound
+  // variable, but it might be shadowed by variable bindings introduced by
+  // non-strict 'eval' calls between the reference scope (inclusive) and the
+  // binding scope (exclusive).
   Variable* local_if_not_shadowed_;
 
   // Valid as a LHS? (const and this are not valid LHS, for example)
   bool is_valid_LHS_;
 
   // Usage info.
   bool is_accessed_from_inner_scope_;  // set by variable resolver
   bool is_used_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_VARIABLES_H_