Migrate FeedbackUploader to SimpleURLLoader.

This is a copy of https://crrev.com/c/1067424 but with tests fixed.

Bug: 844932
Change-Id: I77239bf76a673b33d56b8b7fe584a78ec319bc24
Reviewed-on: https://chromium-review.googlesource.com/1114253
Commit-Queue: Robbie McElrath <rmcelrath@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#573467}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: d956f867578f34f99d408298f50c10862b24715e
10 files changed