Move out DidStartProvisionalLoad from WebContentsImpl into Navigator.

content/browser/renderer_host/frame_tree.h

Index: content/browser/renderer_host/frame_tree.h
diff --git a/content/browser/renderer_host/frame_tree.h b/content/browser/renderer_host/frame_tree.h
index 8c452e93e5d7fb70b742baaf9c6933c62815fcac..c042acdaa003b4d7d6486814a15c42e557f1d7ca 100644
--- a/content/browser/renderer_host/frame_tree.h
+++ b/content/browser/renderer_host/frame_tree.h
@@ -15,6 +15,9 @@
 namespace content {
 
 class FrameTreeNode;
+class NavigationControllerImpl;
+class Navigator;
+class NavigatorObserver;
 class RenderProcessHost;
 class RenderViewHostImpl;
 
@@ -38,6 +41,13 @@ class CONTENT_EXPORT FrameTree {
   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);
 
@@ -85,16 +95,27 @@ class CONTENT_EXPORT FrameTree {
 
   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);
 };