Upstream seems to have completed the whole migration to an opaque
`FrameTreeNodeId`. This change converts all the places that were using
an `int` still.
Chromium change:
https://chromium.googlesource.com/chromium/src/+/e4de125f43660ff1f41e36fbff545c3bf2a7e401
commit e4de125f43660ff1f41e36fbff545c3bf2a7e401
Author: Avi Drissman <avi@chromium.org>
Date: Thu Sep 5 00:15:45 2024 +0000
Use an opaque type for FrameTreeNode IDs, part 15
content/public
Bug: 361344235
Pavel Beloborodov