Remove ThirdPartyIframeRedirectBlockingEnabled preference

https://bugs.webkit.org/show_bug.cgi?id=265196

Reviewed by Timothy Hatcher.

* Source/WTF/Scripts/Preferences/UnifiedWebPreferences.yaml:
* Source/WebCore/dom/Document.cpp:
(WebCore::Document::isNavigationBlockedByThirdPartyIFrameRedirectBlocking):

Canonical link: https://commits.webkit.org/271041@main

Source/WTF/Scripts/Preferences/UnifiedWebPreferences.yaml

@@ -6568,19 +6568,6 @@ TextRecognitionInVideosEnabled:
     WebKit:
       default: defaultTextRecognitionInVideosEnabled()
 
-ThirdPartyIframeRedirectBlockingEnabled:
-  type: bool
-  status: mature
-  humanReadableName: "Block top-level redirects by third-party iframes"
-  humanReadableDescription: "Block top-level redirects by third-party iframes"
-  defaultValue:
-    WebKitLegacy:
-      default: true
-    WebKit:
-      default: true
-    WebCore:
-      default: true
-
 ThreadedAnimationResolutionEnabled:
   type: bool
   status: unstable

Source/WebCore/dom/Document.cpp

@@ -4033,9 +4033,6 @@ void Document::willLoadFrameElement(const URL& frameURL)
 // Prevent cross-site top-level redirects from third-party iframes unless the user has ever interacted with the frame.
 bool Document::isNavigationBlockedByThirdPartyIFrameRedirectBlocking(LocalFrame& targetFrame, const URL& destinationURL)
 {
-    if (!settings().thirdPartyIframeRedirectBlockingEnabled())
-        return false;
-
     // Only prevent top frame navigations by subframes.
     if (m_frame == &targetFrame || &targetFrame != &m_frame->tree().top())
         return false;