Remove old session history logic.

content/browser/frame_host/frame_navigation_entry.cc

Index: content/browser/frame_host/frame_navigation_entry.cc
diff --git a/content/browser/frame_host/frame_navigation_entry.cc b/content/browser/frame_host/frame_navigation_entry.cc
index 5ebb6c29047d87e5ead0d369657015af217d22db..3a46ef6fb06317219ddf6ace5b567b1bf563b6f2 100644
--- a/content/browser/frame_host/frame_navigation_entry.cc
+++ b/content/browser/frame_host/frame_navigation_entry.cc
@@ -99,7 +99,6 @@ void FrameNavigationEntry::SetPageState(const PageState& page_state) {
 
 scoped_refptr<ResourceRequestBodyImpl> FrameNavigationEntry::GetPostData()
     const {
-  DCHECK(SiteIsolationPolicy::UseSubframeNavigationEntries());
   if (method_ != "POST")
     return nullptr;