Revert of Don't mark navigations as in-page when DSNs are mismatched.

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 6276bf6ca0646af488829afddc4d00dba6122a61..cb9e3d3faa5df2dc38de129057f07c3d243797bb 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -5530,16 +5530,12 @@
 
         // If this is marked as a same document load but we haven't committed
         // anything, treat it as a new load.  The browser shouldn't let this
-        // happen. Also treat it as a new load, if the DSN in
-        // |current_history_item_| and the item navigated to mismatch.
-        if (history_load_type == blink::WebHistorySameDocumentLoad) {
-           if (current_history_item_.isNull()) {
-             history_load_type = blink::WebHistoryDifferentDocumentLoad;
-           } else if (current_history_item_.documentSequenceNumber() !=
-                      item_for_history_navigation.documentSequenceNumber()) {
-             history_load_type = blink::WebHistoryDifferentDocumentLoad;
-             NOTREACHED();
-           }
+        // happen.
+        // TODO(creis): Add a similar check if the DSN doesn't match, and add a
+        // NOTREACHED when we're confident this won't happen.
+        if (history_load_type == blink::WebHistorySameDocumentLoad &&
+            current_history_item_.isNull()) {
+          history_load_type = blink::WebHistoryDifferentDocumentLoad;
         }
 
         // If this navigation is to a history item for a new child frame, we may