Parse harmony let declarations.

src/scanner-base.h

Index: src/scanner-base.h
diff --git a/src/scanner-base.h b/src/scanner-base.h
index d3776e5f8996719561bd037f6c764e28171608d0..3e1772a3d237f1cd4a03f9c3757e56b45afafdd6 100644
--- a/src/scanner-base.h
+++ b/src/scanner-base.h
@@ -507,6 +507,14 @@ class JavaScriptScanner : public Scanner {
   // tokens, which is what it is used for.
   void SeekForward(int pos);
 
+  bool HarmonyBlockScoping() const {
+    return harmony_block_scoping_;
+  }
+  void SetHarmonyBlockScoping(bool block_scoping) {
+    harmony_block_scoping_ = block_scoping;
+  }
+
+
  protected:
   bool SkipWhiteSpace();
   Token::Value SkipSingleLineComment();
@@ -540,6 +548,9 @@ class JavaScriptScanner : public Scanner {
   // Whether there is a multi-line comment that contains a
   // line-terminator after the current token, and before the next.
   bool has_multiline_comment_before_next_;
+  // Whether we scan 'let' as a keyword for harmony block scoped
+  // let bindings.
+  bool harmony_block_scoping_;
 };
 
 } }  // namespace v8::internal