00a0acf5827cf00a92eb57e4b5d3d38859a1e6c7  [Site Isolation] Clicking a selection in a cross-origin iframe in a background window only activates the window

Classified as not security-relevant.
Triage note: Changes HandleAcceptsFirstMouse/ShouldDelayWindowOrderingEvent IPC to carry Variant<bool, RemoteUserInputEventData> and loops hit-testing into remote subframes via frameForFirstMouseHitTest. This is site-isolation feature plumbing for cross-process first-mouse handling, not a memory-safety or logic vuln fix.
This commit was flagged by the signal scorer and reviewed by AI (not a human). It is listed only so the triage is auditable; there is no root-cause analysis because this is not a vulnerability fix.

Structural signals: smartptr_member_added (+6.47), null_guard (+2.59)