Some code in type-info.cc could allow a cross context map to be visible to
crankshaft. Tighten up this code to be certain that only a JSFunction, an
AllocationSite or a Symbol can be returned.

R=verwaest@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1026343004

Cr-Commit-Position: refs/heads/master@{#27417}