Remove --experimental-classes flag and related dead code.

src/preparser.h

 // Copyright 2012 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.
 
 #ifndef V8_PREPARSER_H
 #define V8_PREPARSER_H
 
 #include "src/v8.h"
 
 #include "src/bailout-reason.h"
@@ skipping 301 matching lines @@
   };
 
   Scope* NewScope(Scope* parent, ScopeType scope_type,
                   FunctionKind kind = kNormalFunction) {
     DCHECK(ast_value_factory());
     DCHECK(scope_type != MODULE_SCOPE || allow_harmony_modules());
     DCHECK((scope_type == FUNCTION_SCOPE && IsValidFunctionKind(kind)) ||
            kind == kNormalFunction);
     Scope* result =
         new (zone()) Scope(zone(), parent, scope_type, ast_value_factory());
-    bool uninitialized_this =
-        FLAG_experimental_classes && IsSubclassConstructor(kind);
+    bool uninitialized_this = IsSubclassConstructor(kind);
     result->Initialize(uninitialized_this);
     return result;
   }
 
   Scanner* scanner() const { return scanner_; }
   AstValueFactory* ast_value_factory() const { return ast_value_factory_; }
   int position() { return scanner_->location().beg_pos; }
   int peek_position() { return scanner_->peek_location().beg_pos; }
   bool stack_overflow() const { return stack_overflow_; }
   void set_stack_overflow() { stack_overflow_ = true; }
@@ skipping 2745 matching lines @@
       *ok = false;
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H