Remove legacy features histogram from blink

Tests for counting features are removed from the blink side because
there are browser side testing them, please see:
chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc

Tests for frame fetch context is removed, but there's still test
coverage in
chromium/src/chrome/browser/client_hints/client_hints_browsertest.cc

Tests for blink side use counter dropping ntp activities is no longer
needed as blink side use counter is being removed.

TBR: nhiroki@chromium.org
Bug: 849695, 790957
Change-Id: I32b0d01b768c7043fb01f2329cc089049126ed2b
Reviewed-on: https://chromium-review.googlesource.com/1087045
Commit-Queue: Luna Lu <loonybear@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Rick Byers <rbyers@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567259}
7 files changed