Don't update subframes on parent frame commits.

content/renderer/history_controller.cc

 // Copyright 2014 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.
 
 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  *     (http://www.torchmobile.com/)
  *
@@ skipping 126 matching lines @@
       current_entry_->GetItemForFrame(render_frame);
   if (new_item.isNull())
     return;
 
   if (old_item.isNull() ||
       new_item.itemSequenceNumber() != old_item.itemSequenceNumber()) {
     if (!old_item.isNull() &&
         new_item.documentSequenceNumber() ==
             old_item.documentSequenceNumber()) {
       same_document_loads.push_back(std::make_pair(frame, new_item));
+
+      // Returning here (and omitting child frames which have also changed) is
+      // wrong, but not returning here is worse. See the discussion in
+      // NavigationControllerImpl::FindFramesToNavigate for more information.
+      return;
     } else {
       different_document_loads.push_back(std::make_pair(frame, new_item));
       // For a different document, the subframes will be destroyed, so there's
       // no need to consider them.
       return;
     }
   }
 
   for (WebFrame* child = frame->firstChild(); child;
        child = child->nextSibling()) {
@@ skipping 120 matching lines @@
     bool clone_children_of_target) {
   if (!current_entry_) {
     current_entry_.reset(new HistoryEntry(new_item));
   } else {
     current_entry_.reset(current_entry_->CloneAndReplace(
         new_item, clone_children_of_target, target_frame, render_view_));
   }
 }
 
 }  // namespace content