Migrate SafeSearchURLChecker to SimpleURLLoader

Bug: 773295
Change-Id: I6be6adefab29b5d4e67013f45ba5ffe4e058dbdc
Reviewed-on: https://chromium-review.googlesource.com/1030062
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Mark Pilgrim <pilgrim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558725}
7 files changed