RenderHostImpl::AddRoute - Turn a DCHECK to CHECK()

This is to narrow down the cause of a crash bug and
likely to crash. Please revert and let me know
if you see this in the wild.

R=nasko@chromium.org, kareng@chromium.org
BUG=381990, 415059

Review URL: https://codereview.chromium.org/657613003

Cr-Commit-Position: refs/heads/master@{#299591}
1 file changed