[es6] Reintroduce the instanceof operator in the backends.

src/parsing/parser-base.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_PARSING_PARSER_BASE_H
 #define V8_PARSING_PARSER_BASE_H
 
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
 #include "src/hashmap.h"
@@ skipping 2543 matching lines @@
       // operations.  (We could combine the two and get rid of this
       // code and AST node eventually.)
       if (Token::IsCompareOp(op)) {
         // We have a comparison.
         Token::Value cmp = op;
         switch (op) {
           case Token::NE: cmp = Token::EQ; break;
           case Token::NE_STRICT: cmp = Token::EQ_STRICT; break;
           default: break;
         }
-        if (FLAG_harmony_instanceof && cmp == Token::INSTANCEOF) {
-          x = Traits::RewriteInstanceof(x, y, pos);
-        } else {
-          x = factory()->NewCompareOperation(cmp, x, y, pos);
-          if (cmp != op) {
-            // The comparison was negated - add a NOT.
-            x = factory()->NewUnaryOperation(Token::NOT, x, pos);
-          }
+        x = factory()->NewCompareOperation(cmp, x, y, pos);
+        if (cmp != op) {
+          // The comparison was negated - add a NOT.
+          x = factory()->NewUnaryOperation(Token::NOT, x, pos);
         }
-
       } else if (op == Token::EXP) {
         x = Traits::RewriteExponentiation(x, y, pos);
       } else {
         // We have a "normal" binary operation.
         x = factory()->NewBinaryOperation(op, x, y, pos);
       }
     }
   }
   return x;
 }
@@ skipping 1008 matching lines @@
     has_seen_constructor_ = true;
     return;
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H