Turn cross-origin downloads into navigations

BUG=831073
R=qinmin@chromium.org,clamy@chromium.org

Change-Id: I1c07cd89e06a8b15272ff862d237da5527288b7a
Reviewed-on: https://chromium-review.googlesource.com/1138081
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Min Qin <qinmin@chromium.org>
Reviewed-by: Camille Lamy <clamy@chromium.org>
Commit-Queue: Jochen Eisinger <jochen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576376}
17 files changed