Parser: Fix InitializerRewriter.

The bug was caused by AstTraversalVisitor refactoring:
https://codereview.chromium.org/2169833002/

InitializerRewriter::VisitRewritableExpression in parser.cc didn't recurse; so
it fails when a rewritable expression contains another rewritable expression.

See the bug for more details.

BUG=chromium:679727

Review-Url: https://codereview.chromium.org/2629623002
Cr-Commit-Position: refs/heads/master@{#42274}

src/parsing/parser.cc

@@ -2839,6 +2839,7 @@ class InitializerRewriter final
     if (to_rewrite->is_rewritten()) return;
     Parser::PatternRewriter::RewriteDestructuringAssignment(parser_, to_rewrite,
                                                             scope_);
+    AstTraversalVisitor::VisitRewritableExpression(to_rewrite);
   }
 
   // Code in function literals does not need to be eagerly rewritten, it will be

test/mjsunit/regress/regress-679727.js

@@ -0,0 +1,6 @@
+// Copyright 2017 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.
+
+f = (e=({} = {} = 1)) => {}; f(1);
+((e = ({} = {} = {})) => {})(1)