Remove old session history logic.

content/common/site_isolation_policy.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_COMMON_SITE_ISOLATION_POLICY_H_
 #define CONTENT_COMMON_SITE_ISOLATION_POLICY_H_
 
 #include "base/macros.h"
 #include "content/common/content_export.h"
 #include "url/gurl.h"
@@ skipping 23 matching lines @@
   // particular site merits protection.
   static bool AreCrossProcessFramesPossible();
 
   // Returns true if every site should be placed in a dedicated process.
   static bool UseDedicatedProcessesForAllSites();
 
   // Returns true if third-party subframes of a page should be kept in a
   // different process from the main frame.
   static bool IsTopDocumentIsolationEnabled();
 
-  // Returns true if navigation and history code should maintain per-frame
-  // navigation entries. This is an in-progress feature related to site
-  // isolation, so the return value is currently tied to --site-per-process.
-  // TODO(creis, avi): Make this the default, and eliminate this.
-  static bool UseSubframeNavigationEntries();
-
  private:
   SiteIsolationPolicy();  // Not instantiable.
 
   DISALLOW_COPY_AND_ASSIGN(SiteIsolationPolicy);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_SITE_ISOLATION_POLICY_H_