Tell renderer which subframes have history items on back/forward.

content/renderer/render_frame_impl.h

 // Copyright 2013 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_RENDERER_RENDER_FRAME_IMPL_H_
 #define CONTENT_RENDERER_RENDER_FRAME_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 1078 matching lines @@
   // Non-null when the RenderFrame is a local root for compositing, input,
   // layout, etc. A local frame is also a local root iff it does not have a
   // parent that is a local frame.
   scoped_refptr<RenderWidget> render_widget_;
 
   // Temporarily holds state pertaining to a navigation that has been initiated
   // until the NavigationState corresponding to the new navigation is created in
   // didCreateDataSource().
   std::unique_ptr<NavigationParams> pending_navigation_params_;
 
-  // Keeps track of whether the browser process has any history items that need
-  // to be used for subframes of this frame (in the case of a history
-  // navigation).  If not, the renderer can skip sending an IPC to the browser
-  // and directly load any initial URLs for children itself.  This state is
-  // cleared during didStopLoading, since it is not needed after the first load
-  // completes and is never used after the initial navigation.  It is inherited
-  // by subframes.
-  // TODO(creis): Switch this to a data structure of unique names and
-  // corresponding same-process PageStates in https://crbug.com/639842.
-  bool browser_has_subtree_history_items_;
+  // Keeps track of which future subframes the browser process has history items
+  // for during a history navigation.  The renderer process should ask the
+  // browser for history items when subframes with these names are created, and
+  // directly load the initial URLs for any other subframes.  This state is
+  // incrementally cleared as it is used and then reset in didStopLoading, since
+  // it is not needed after the first load completes and is never used after the
+  // initial navigation.
+  // TODO(creis): Expand this to include any corresponding same-process
+  // PageStates for the whole subtree in https://crbug.com/639842.
+  std::set<std::string> history_subframe_unique_names_;
 
   // Stores the current history item for this frame, so that updates to it can
   // be reported to the browser process via SendUpdateState.
   blink::WebHistoryItem current_history_item_;
 
 #if defined(ENABLE_PLUGINS)
   // Current text input composition text. Empty if no composition is in
   // progress.
   base::string16 pepper_composition_text_;
 
@@ skipping 182 matching lines @@
       remote_associated_interfaces_;
 
   base::WeakPtrFactory<RenderFrameImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_FRAME_IMPL_H_