Add language detection content browser test including nested nodes.

R=dmazzoni,aboxhall

Bug: 889370
Change-Id: I56bd50586a13d754d9dd1547e277d7daab216ec3
Reviewed-on: https://chromium-review.googlesource.com/c/1362698
Commit-Queue: Chris Hall <chrishall@chromium.org>
Reviewed-by: Alice Boxhall <aboxhall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614252}
6 files changed