Ensure we properly set PageTransition for iframes.

We currently don't set subframe navigations as manual when it isn't the first
navigation of the iframe. Also, we don't propagate the state correctly in the
case of a cross-process transition.

BUG=464014

Review URL: https://codereview.chromium.org/1002953004

Cr-Commit-Position: refs/heads/master@{#326404}
9 files changed