[strong] Make strong 'this' optional for experimentation

src/preparser.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 <cmath>
 
 #include "src/allocation.h"
 #include "src/base/logging.h"
 #include "src/conversions-inl.h"
 #include "src/conversions.h"
@@ skipping 581 matching lines @@
   switch (peek()) {
     case Token::FUNCTION:
     case Token::LBRACE:
       UNREACHABLE();  // Always handled by the callers.
     case Token::CLASS:
       ReportUnexpectedToken(Next());
       *ok = false;
       return Statement::Default();
 
     case Token::THIS:
+      if (!FLAG_strong_this) break;

[Dmitry Lomov (no reviews), 2015/06/15 11:52:52]

Please add: 
 // Fall through.

     case Token::SUPER:
       if (is_strong(language_mode()) &&
           i::IsConstructor(function_state_->kind())) {
         bool is_this = peek() == Token::THIS;
         Expression expr = Expression::Default();
         ExpressionClassifier classifier;
         if (is_this) {
           expr = ParseStrongInitializationExpression(&classifier, CHECK_OK);
         } else {
           expr = ParseStrongSuperCallExpression(&classifier, CHECK_OK);
@@ skipping 572 matching lines @@
 
   DCHECK(!spread_pos.IsValid());
 
   return Expression::Default();
 }
 
 #undef CHECK_OK
 
 
 } }  // v8::internal