Apply iframe referrerpolicy attribute to non-initial loads.

Bug: 967095
Change-Id: I85ffd419c43f4715ce6fcf9857b08d340d605554
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1629287
Reviewed-by: Nate Chapin <japhet@chromium.org>
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663964}
2 files changed