Move DownloadUrlLoaderFactoryGetterImpl from content/ to components/

There are no dependencies in content/ for this class.
Moving it to components/ so it can be used in chrome/ layer for servicification.

BUG=695115

Change-Id: If37805b71ef588bbaaa7035eecb16c5cbc4a75b6
Reviewed-on: https://chromium-review.googlesource.com/1150402
Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Min Qin <qinmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578071}
6 files changed