Create a new RenderFrameHost per child frame when --site-per-process is enabled.

content/browser/renderer_host/frame_tree.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_BROWSER_RENDERER_HOST_FRAME_TREE_H_
+#define CONTENT_BROWSER_RENDERER_HOST_FRAME_TREE_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "base/memory/scoped_ptr.h"
+#include "content/browser/renderer_host/frame_tree_node.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+class FrameTreeNode;
+class RenderProcessHost;
+
+// Represents the frame tree for a page. With the exception of the main frame,
+// all FrameTreeNodes will be created/deleted in response to frame attach and
+// detach events in the DOM.
+//
+// The main frame's FrameTreeNode is special in that it is reused. This allows
+// it to serve as an anchor for state that needs to persist across top-level
+// page navigations.
+//
+// TODO(ajwong): Move NavigationController ownership the to main frame
+// FrameTreeNode. Possibly expose access to it from here.
+//
+// This object is only used on the UI thread.
+class CONTENT_EXPORT FrameTree {

[Charlie Reis, 2013/09/24 18:25:58]

Can you add something to the class comment about the fact that this will only
contain FrameTreeNodes for subframes if the --site-per-process flag is passed? 
I know there are current uses of FrameTreeNodes (e.g., UMA stats) and future
planned uses (e.g., possibly cross-site document blocking) that will be affected
by this.

[awong, 2013/09/26 21:25:24]

Done.

+ public:
+  FrameTree();
+  ~FrameTree();
+
+  // Returns the FrameTreeNode with the given |frame_id|.
+  FrameTreeNode* FindByID(int64 frame_id);
+
+  // Executes |on_node| on each node in the frame tree.  If |on_node| returns
+  // false, terminates the iteration immediately. Returning false is useful
+  // if |on_node| is just doing a search over the tree.
+  void ForEach(const base::Callback<bool(FrameTreeNode*)>& on_node) const;
+
+  // After the FrameTree is created, or after SwapMainFrame() has been called,
+  // the root node does not yet have a frame id. This is allocated by the
+  // renderer and is published to the browser process on the first navigation
+  // after a swap. These two functions are used to set the root node's frame
+  // id.
+  //
+  // TODO(ajwong): Remove these once RenderFrameHost's routing id replaces
+  // frame_id.
+  bool IsFirstNavigationAfterSwap() const;
+  void OnFirstNavigationAfterSwap(int main_frame_id);
+
+  // Frame tree manipulation routines.
+  void AddFrame(int render_frame_host_id, int64 parent_frame_id,
+                int64 frame_id, const std::string& frame_name);
+  void RemoveFrame(int64 parent_frame_id, int64 frame_id);
+  void SetFrameUrl(int64 frame_id, const GURL& url);
+
+  // Resets the FrameTree and changes RenderFrameHost for the main frame.
+  // This destroys most of frame tree but retains the root node so that
+  // navigation state may be kept on it between process swaps. Used to
+  // support bookeeping for top-level navigations.
+  //
+  // If |main_frame| is NULL, reset tree to initially constructed state.
+  //
+  // TODO(ajwong): This function should not be given a |main_frame|. This is
+  // required currently because the RenderViewHost owns is main frame. When

[Charlie Reis, 2013/09/24 18:25:58]

nit: owns its

[awong, 2013/09/26 21:25:24]

Done.

+  // that relation is fixed, the FrameTree should be repsonsible for

[Charlie Reis, 2013/09/24 18:25:58]

nit: responsible

[awong, 2013/09/26 21:25:24]

Done.

+  // created/destroying the main frame on the swap.
+  void SwapMainFrame(RenderFrameHostImpl* main_frame);
+
+  // Convenience accessor for the main frame's RenderFrameHostImpl.
+  RenderFrameHostImpl* GetMainFrame() const;
+
+  // Allows a client to listen for frame removal.
+  void SetFrameRemoveListener(
+      const base::Callback<void(int64)>& on_frame_removed);
+
+  FrameTreeNode* GetRootForTesting() { return root_.get(); }
+
+ private:
+  scoped_ptr<FrameTreeNode> CreateNode(int64 frame_id,
+                                       const std::string& frame_name,
+                                       int render_frame_host_id,
+                                       RenderProcessHost* render_process_host);
+
+  scoped_ptr<FrameTreeNode> root_;
+
+  base::Callback<void(int64)> on_frame_removed_;
+
+  DISALLOW_COPY_AND_ASSIGN(FrameTree);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_FRAME_TREE_H_