Make native syntax an early error in the preparser.

src/scanner.h

Index: src/scanner.h
diff --git a/src/scanner.h b/src/scanner.h
index 6651c3875539a600ce9e391144495104249f6bc0..a2e64a9d2000125a05167034f41026881bc44988 100644
--- a/src/scanner.h
+++ b/src/scanner.h
@@ -41,6 +41,17 @@
 namespace v8 {
 namespace internal {
 
+
+// General collection of bit-flags that can be passed to scanners and
+// parsers to signify their (initial) mode of operation.
+enum ParsingFlags {
+  kNoParsingFlags = 0,
+  kAllowLazy = 1,
+  kAllowNativesSyntax = 2,
+  kHarmonyScoping = 4
+};
+
+
 // Returns the value (0 .. 15) of a hexadecimal character c.
 // If c is not a legal hexadecimal character, returns a value < 0.
 inline int HexValue(uc32 c) {