Bug 309110 – [Site Isolation] Support cross-site process swap for UIProcess-driven back/forward child frame navigation.

• Component: New Bugs
• Status: RESOLVED FIXED

[Basuke Suzuki]

This is a follow-up to https://bugs.webkit.org/show_bug.cgi?id=308562 which routed same-site child frame back/forward navigations through UIProcess when UseUIProcessForBackForwardItemLoading is enabled.

When a child frame's back/forward navigation requires a cross-site process swap, send GoToBackForwardItem with the child frame's FrameState to the new process so it can perform a proper history navigation with full state restoration (scroll position, form data, session state, etc.) instead of a plain LoadRequest.

In decidePolicyForNavigationAction, the FrameState found for back/forward child frame navigations is now stored on the Navigation object in addition to the PolicyDecision. This allows continueNavigationInNewProcess to retrieve it when a process swap is needed. The two consumers are mutually exclusive: the completionHandler sets it on PolicyDecision for same-site navigations (PolicyAction::Use), while the Navigation object carries it for cross-site process swaps (PolicyAction::LoadWillContinueInAnotherProcess).

[Basuke Suzuki]

rdar://171032434

[Basuke Suzuki]

Pull request: https://github.com/WebKit/WebKit/pull/59896

[Basuke Suzuki]

Pull request: https://github.com/WebKit/WebKit/pull/59925

[EWS]

Committed 308761@main (95087ee3081b): <https://commits.webkit.org/308761@main>

Reviewed commits have been landed. Closing PR #59896 and removing active labels.