From the Google C++ style guide: "You may not use a using-directive to
make all names from a namespace available". This would be covered by
presubmit linter checks if build/namespaces were not blacklisted.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/1410073004

Cr-Commit-Position: refs/heads/master@{#31565}