Implement proper scoping for "this" in arrow functions

src/variables.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/ast.h"
 #include "src/scopes.h"
 #include "src/variables.h"
 
@@ skipping 14 matching lines @@
     case DYNAMIC_LOCAL: return "DYNAMIC_LOCAL";
     case INTERNAL: return "INTERNAL";
     case TEMPORARY: return "TEMPORARY";
   }
   UNREACHABLE();
   return NULL;
 }
 
 
 Variable::Variable(Scope* scope, const AstRawString* name, VariableMode mode,
-                   bool is_valid_ref, Kind kind,
-                   InitializationFlag initialization_flag,
+                   Kind kind, InitializationFlag initialization_flag,
                    MaybeAssignedFlag maybe_assigned_flag)
     : scope_(scope),
       name_(name),
       mode_(mode),
       kind_(kind),
       location_(UNALLOCATED),
       index_(-1),
       initializer_position_(RelocInfo::kNoPosition),
       local_if_not_shadowed_(NULL),
-      is_valid_ref_(is_valid_ref),
       force_context_allocation_(false),
       is_used_(false),
       initialization_flag_(initialization_flag),
       maybe_assigned_(maybe_assigned_flag) {
   // Var declared variables never need initialization.
   DCHECK(!(mode == VAR && initialization_flag == kNeedsInitialization));
 }
 
 
 bool Variable::IsGlobalObjectProperty() const {
   // Temporaries are never global, they must always be allocated in the
   // activation frame.
   return (IsDynamicVariableMode(mode_) ||
           (IsDeclaredVariableMode(mode_) && !IsLexicalVariableMode(mode_)))
       && scope_ != NULL && scope_->is_script_scope();
 }
 
 
 int Variable::CompareIndex(Variable* const* v, Variable* const* w) {
   int x = (*v)->index();
   int y = (*w)->index();
   // Consider sorting them according to type as well?
   return x - y;
 }
 
 } }  // namespace v8::internal