Resolve references to "this" the same way as normal variables

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index 056d34a42faf80946de4c9f5a1a43ce0930c8d66..d3ac57e4fe6731a5a6132d27a2fab773b98a295b 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -739,7 +739,9 @@ const AstRawString* ParserTraits::GetNextSymbol(Scanner* scanner) {
 
 Expression* ParserTraits::ThisExpression(Scope* scope, AstNodeFactory* factory,
                                          int pos) {
-  return factory->NewVariableProxy(scope->receiver(), pos);
+  return scope->NewUnresolved(factory,
+                              parser_->ast_value_factory()->this_string(), pos,
+                              pos + 4, Variable::THIS);
 }
 
 Expression* ParserTraits::SuperReference(Scope* scope, AstNodeFactory* factory,