Move out DidStartProvisionalLoad from WebContentsImpl into Navigator.

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 NavigationControllerImpl;
+class Navigator;
+class NavigatorObserver;
 class RenderProcessHost;
 class RenderViewHostImpl;
 
 // 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 to the main frame
 // FrameTreeNode. Possibly expose access to it from here.
 //
 // TODO(ajwong): Currently this class only contains FrameTreeNodes for
 // subframes if the --site-per-process flag is enabled.
 //
 // This object is only used on the UI thread.
 class CONTENT_EXPORT FrameTree {
  public:
   FrameTree();
   ~FrameTree();
 
+  // Initializes the frame tree with a NavigationController which keeps
+  // session history for it and NavigationObserver which dispatches

[Charlie Reis, 2013/10/17 00:17:25]

This doesn't seem to match the observer pattern, where multiple objects could
register to observe events dispatched by Navigator.  It sounds like you're using
it more like a delegate.

+  // notifications for navigation events.
+  void Init(
+      NavigationControllerImpl* navigation_controller,
+      NavigatorObserver* navigator_observer);
+
   // 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
@@ skipping 27 matching lines @@
 
   // 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(RenderViewHostImpl*, int64)>& on_frame_removed);
 
   FrameTreeNode* GetRootForTesting() { return root_.get(); }
 
+  Navigator* navigator() {
+    return navigator_.get();
+  }
+
  private:
   scoped_ptr<FrameTreeNode> CreateNode(int64 frame_id,
                                        const std::string& frame_name,
                                        int render_frame_host_id,
                                        RenderProcessHost* render_process_host);
 
+  // The root node for the frame tree.
   scoped_ptr<FrameTreeNode> root_;
 
+  // Callback which is invoked when a FrameTreeNode is removed from the
+  // tree.
   base::Callback<void(RenderViewHostImpl*, int64)> on_frame_removed_;
 
+  // This is passed in to all FrameTreeNode objects which use it for
+  // performing navigations.
+  scoped_ptr<Navigator> navigator_;
+
   DISALLOW_COPY_AND_ASSIGN(FrameTree);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_FRAME_TREE_H_