[es6] Spread in array literals

src/preparser.h

Index: src/preparser.h
diff --git a/src/preparser.h b/src/preparser.h
index c14fb9b20cdc067c3f37b86938138aa648b73daa..d38aaaaa26e7f1fa3876c041b708d123c054660a 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -123,6 +123,9 @@ class ParserBase : public Traits {
   bool allow_harmony_destructuring() const {
     return allow_harmony_destructuring_;
   }
+  bool allow_harmony_spread_arrays() const {
+    return allow_harmony_spread_arrays_;
+  }
 
   bool allow_strong_mode() const { return allow_strong_mode_; }
 
@@ -161,7 +164,9 @@ class ParserBase : public Traits {
   void set_allow_harmony_destructuring(bool allow) {
     allow_harmony_destructuring_ = allow;
   }
-
+  void set_allow_harmony_spread_arrays(bool allow) {
+    allow_harmony_spread_arrays_ = allow;
+  }
 
  protected:
   enum AllowRestrictedIdentifiers {
@@ -1011,6 +1016,7 @@ class ParserBase : public Traits {
   bool allow_harmony_rest_params_;
   bool allow_harmony_spreadcalls_;
   bool allow_harmony_destructuring_;
+  bool allow_harmony_spread_arrays_;
   bool allow_strong_mode_;
 };
 
@@ -2508,12 +2514,13 @@ typename ParserBase<Traits>::ExpressionT ParserBase<Traits>::ParseArrayLiteral(
       }
       elem = this->GetLiteralTheHole(peek_position(), factory());
     } else if (peek() == Token::ELLIPSIS) {
-      ExpressionUnexpectedToken(classifier);
+      if (!allow_harmony_spread_arrays()) {
+        ExpressionUnexpectedToken(classifier);
+      }
       int start_pos = peek_position();
       Consume(Token::ELLIPSIS);
       ExpressionT argument =
           this->ParseAssignmentExpression(true, classifier, CHECK_OK);
-
       elem = factory()->NewSpread(argument, start_pos);
       seen_spread = true;
     } else {