Trigger heavy ad intervention when an unloaded heavy ad navigates

Bug: 1099014
Change-Id: I98a2d0e548a48fd93618fbae1c1d458f1dbd58a4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2269740


Reviewed-by: John Delaney <johnidel@chromium.org>
Commit-Queue: Andrew Paseltiner <apaseltiner@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791488}