[es6] emit error when for-in loop declarations are initialized in strict mode

src/preparser.h

Index: src/preparser.h
diff --git a/src/preparser.h b/src/preparser.h
index 92c762d36bcbbe4930bfac5fdeee1b1cae197a26..35b65853b3f553560df54e873043ea26efc2d128 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -162,9 +162,6 @@ class ParserBase : public Traits {
     kForStatement
   };
 
-  // If a list of variable declarations includes any initializers.
-  enum VariableDeclarationProperties { kHasInitializers, kHasNoInitializers };
-
   class Checkpoint;
   class ObjectLiteralCheckerBase;
 
@@ -1588,8 +1585,8 @@ class PreParser : public ParserBase<PreParserTraits> {
   Statement ParseVariableStatement(VariableDeclarationContext var_context,
                                    bool* ok);
   Statement ParseVariableDeclarations(VariableDeclarationContext var_context,
-                                      VariableDeclarationProperties* decl_props,
                                       int* num_decl,
+                                      Scanner::Location* first_initializer_loc,
                                       bool* ok);
   Statement ParseExpressionOrLabelledStatement(bool* ok);
   Statement ParseIfStatement(bool* ok);