Implement proper scoping for "this" in arrow functions

src/ast.cc

Index: src/ast.cc
diff --git a/src/ast.cc b/src/ast.cc
index ac81e751afb31f1ea89e8e47ac1cd68c6b198e2b..0a9e7838c2eb4216cfe20673e1d7af6a3d963179 100644
--- a/src/ast.cc
+++ b/src/ast.cc
@@ -70,11 +70,13 @@ VariableProxy::VariableProxy(Zone* zone, Variable* var, int position)
 }
 
 
-VariableProxy::VariableProxy(Zone* zone, const AstRawString* name, bool is_this,
-                             int position)
+VariableProxy::VariableProxy(Zone* zone, const AstRawString* name,
+                             Variable::Kind variable_kind, int position)
     : Expression(zone, position),
-      bit_field_(IsThisField::encode(is_this) | IsAssignedField::encode(false) |
-                 IsResolvedField::encode(false)),
+      bit_field_(
+          IsThisField::encode(variable_kind == Variable::THIS) |
+          IsAssignedField::encode(false) | IsResolvedField::encode(false) |
+          IsNewTargetField::encode(variable_kind == Variable::NEW_TARGET)),
       variable_feedback_slot_(FeedbackVectorICSlot::Invalid()),
       raw_name_(name) {}