PM: Add change notification on frame URL changes.

Change-Id: I53e12a84340df56e24bc78abddf479e109a7aba0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617085
Commit-Queue: Chris Hamilton <chrisha@chromium.org>
Reviewed-by: Chris Hamilton <chrisha@chromium.org>
Auto-Submit: Sigurður Ásgeirsson <siggi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661207}
6 files changed