MaterializedLiteral expressions need to cache expression depth.

A problem arises in recursive literal expressions due to recent
changes that defer allocation of constant literal properties
from parse time. We were calculating expression depth as a
side-effect of a lazy constant property build, but subsequent
calls for the depth always returned 1. Cache the correct depth
in the MaterializedLiteral instead.

(Related-to/very-partial-revert-of
https://codereview.chromium.org/61873003)

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/78493002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17929 ce2b1a6d-e550-0410-aec6-3dcde31c8c00