Track usage of "this" and "arguments" in Scope

src/preparser.h

Index: src/preparser.h
diff --git a/src/preparser.h b/src/preparser.h
index 1c1e1c4520d0e3cad95a6f2cbb3afdec963d02a7..02d44f8af6345bf1dabb4b435dda57b8dded2d88 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -892,6 +892,8 @@ class PreParserScope {
 
   bool IsDeclared(const PreParserIdentifier& identifier) const { return false; }
   void DeclareParameter(const PreParserIdentifier& identifier, VariableMode) {}
+  void RecordArgumentsUsage() {}
+  void RecordThisUsage() {}
 
   // Allow scope->Foo() to work.
   PreParserScope* operator->() { return this; }
@@ -1544,6 +1546,7 @@ typename ParserBase<Traits>::IdentifierT ParserBase<Traits>::ParseIdentifier(
       ReportMessage("strict_eval_arguments");
       *ok = false;
     }
+    if (name->IsArguments()) scope_->RecordArgumentsUsage();
     return name;
   } else if (strict_mode() == SLOPPY &&
              (next == Token::FUTURE_STRICT_RESERVED_WORD ||
@@ -1574,7 +1577,10 @@ typename ParserBase<Traits>::IdentifierT ParserBase<
     *ok = false;
     return Traits::EmptyIdentifier();
   }
-  return this->GetSymbol(scanner());
+
+  IdentifierT name = this->GetSymbol(scanner());
+  if (name->IsArguments()) scope_->RecordArgumentsUsage();
+  return name;
 }
 
 
@@ -1589,7 +1595,10 @@ ParserBase<Traits>::ParseIdentifierName(bool* ok) {
     *ok = false;
     return Traits::EmptyIdentifier();
   }
-  return this->GetSymbol(scanner());
+
+  IdentifierT name = this->GetSymbol(scanner());
+  if (name->IsArguments()) scope_->RecordArgumentsUsage();
+  return name;
 }
 
 
@@ -1666,6 +1675,7 @@ ParserBase<Traits>::ParsePrimaryExpression(bool* ok) {
   switch (token) {
     case Token::THIS: {
       Consume(Token::THIS);
+      scope_->RecordThisUsage();
       result = this->ThisExpression(scope_, factory());
       break;
     }