17704a72d6de2f0e330dff2545ddb68c4bb1f50f  [Site Isolation] Find in Page doesn't locate text inside cross origin iframe on iOS

Classified as not security-relevant.
Triage note: Factors the pathToFrame childFrame() walk into frameContainingRange() and routes decorateTextRangeWithStyle to the containing frame's process instead of a broadcast send(). Site-isolation routing refactor with no identified memory-safety/logic bug.
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), surgical (+1.3)