Introduce AncestorThrottle, which will process 'X-Frame-Options' headers.

This moves the ancestor-based blocking behavior from Blink up into the
browser, and depends on https://codereview.chromium.org/1616943003 for
some infrastructure changes.

BUG=555418
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/1617043002
Cr-Commit-Position: refs/heads/master@{#392032}
26 files changed