ES6: Implement object literal property shorthand

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 2009 matching lines @@
 
     typename Traits::Type::FunctionLiteral value = this->ParseFunctionLiteral(
         name, scanner()->location(),
         false,  // reserved words are allowed here
         FunctionKind::kNormalFunction, RelocInfo::kNoPosition,
         FunctionLiteral::ANONYMOUS_EXPRESSION,
         is_get ? FunctionLiteral::GETTER_ARITY : FunctionLiteral::SETTER_ARITY,
         CHECK_OK_CUSTOM(EmptyObjectLiteralProperty));
     return factory()->NewObjectLiteralProperty(is_get, value, next_pos,
                                                is_static);
+
+  } else if (!in_class && allow_harmony_object_literals_ &&
+             Token::IsIdentifier(name_token, strict_mode(),
+                                 this->is_generator())) {
+    value = this->ExpressionFromIdentifier(name, next_pos, scope_, factory());
+
   } else {
     Token::Value next = Next();
     ReportUnexpectedToken(next);
     *ok = false;
     return this->EmptyObjectLiteralProperty();
   }
 
   uint32_t index;
   LiteralT key = this->IsArrayIndex(name, &index)
                      ? factory()->NewNumberLiteral(index, next_pos)
@@ skipping 789 matching lines @@
       DCHECK(IsAccessorAccessorConflict(old_type, type));
       // Both accessors of the same type.
       parser()->ReportMessage("accessor_get_set");
     }
     *ok = false;
   }
 }
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H