Revert of Ancestors count towards first-partyness.

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index 93ad71a9ecf2d93b25e0ce23347ba706648866b5..fef902a5f5c3d5c032a78b4292bf89db04a492d9 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -3979,26 +3979,6 @@
 
 const KURL& Document::firstPartyForCookies() const
 {
-    if (!RuntimeEnabledFeatures::firstPartyIncludesAncestorsEnabled())
-        return topDocument().url();
-
-    // We're intentionally using the URL of each document rather than the document's SecurityOrigin.
-    // Sandboxing a document into a unique origin shouldn't effect first-/third-party status for
-    // cookies and site data.
-    RefPtr<SecurityOrigin> topOrigin = SecurityOrigin::create(topDocument().url());
-    const Document* currentDocument = this;
-    while (currentDocument) {
-        // Skip over srcdoc documents, as they are always same-origin with their closest non-srcdoc parent.
-        while (currentDocument->isSrcdocDocument())
-            currentDocument = currentDocument->parentDocument();
-        ASSERT(currentDocument);
-
-        if (!topOrigin->canRequest(currentDocument->url()))
-            return SecurityOrigin::urlWithUniqueSecurityOrigin();
-
-        currentDocument = currentDocument->parentDocument();
-    }
-
     return topDocument().url();
 }