Migrate VisitedLinkMaster off of BlockingPool

R=sky@chromium.org

Bug: 667892
Change-Id: Ia354d4cc615983d0ac6650a98a70903484e5ecb8
Reviewed-on: https://chromium-review.googlesource.com/657807
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Brett Wilson <brettw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501424}
2 files changed