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}