Notify the renderer if a history navigation has no subframe items.

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 1072 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_;
+
   // 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_;
 
   PluginPowerSaverHelper* plugin_power_saver_helper_;
@@ skipping 179 matching lines @@
   mojom::FrameHostPtr frame_host_;
 
   base::WeakPtrFactory<RenderFrameImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_FRAME_IMPL_H_