Avoid "using namespace blink" in global scope

With jumbo (unity builds, merged translation units) a "using blink"
statement intended for just the local translation unit will affect
many other translation units which causes various issues.

There is also (with jumbo) a warning about such usage that will prevent
things from compiling.

Without this patch this file will have to be manually excluded from
jumbo builds and I am trying to avoid such exclusion lists for
performance and maintenance.

Review-Url: https://codereview.chromium.org/2965323002
Cr-Commit-Position: refs/heads/master@{#487501}
2 files changed