Send PolicyAction::LoadWillContinueInAnotherProcess if the frame proc…

…ess is changing

https://bugs.webkit.org/show_bug.cgi?id=259863

Reviewed by Tim Horton.

266528@main exposed a bug in the site isolation implementation.
We were sending PolicyAction::LoadWillContinueInAnotherProcess if the load was continuing in a process
other than the initiator, and we should have been sending it if the load was continuing in a process
that is different than the process the frame is in.

This fixes two API tests that were asserting in debug builds:
TestWebKitAPI.SiteIsolation.NavigatingCrossOriginIframeToSameOrigin and
TestWebKitAPI.SiteIsolation.ChildNavigatingToMainFrameDomain

* Source/WebKit/UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::receivedNavigationPolicyDecision):

Canonical link: https://commits.webkit.org/266618@main

Source/WebKit/UIProcess/WebPageProxy.cpp

@@ -3986,7 +3986,7 @@ void WebPageProxy::receivedNavigationPolicyDecision(WebProcessProxy& processNavi
 
         const bool navigationChangesFrameProcess = processNavigatingTo.ptr() != processNavigatingFrom.ptr();
         const bool loadContinuingInNonInitiatingProcess = processInitiatingNavigation.ptr() != processNavigatingTo.ptr();
-        if (loadContinuingInNonInitiatingProcess) {
+        if (navigationChangesFrameProcess) {
             policyAction = PolicyAction::LoadWillContinueInAnotherProcess;
             WEBPAGEPROXY_RELEASE_LOG(ProcessSwapping, "decidePolicyForNavigationAction, swapping process %i with process %i for navigation, reason=%" PUBLIC_LOG_STRING, processID(), processNavigatingTo->processID(), reason.characters());
             LOG(ProcessSwapping, "(ProcessSwapping) Switching from process %i to new process (%i) for navigation %" PRIu64 " '%s'", processID(), processNavigatingTo->processID(), navigation->navigationID(), navigation->loggingString());