RenderFrameDevToolsAgentHost uses new navigation observer API.

content/browser/frame_host/navigation_handle_impl.h

Index: content/browser/frame_host/navigation_handle_impl.h
diff --git a/content/browser/frame_host/navigation_handle_impl.h b/content/browser/frame_host/navigation_handle_impl.h
index 70fb99ed6bc469218bca394b128238c65727ff1d..6f161137b36e7bebc01dfe21ad3a4a8c49840044 100644
--- a/content/browser/frame_host/navigation_handle_impl.h
+++ b/content/browser/frame_host/navigation_handle_impl.h
@@ -11,6 +11,7 @@
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
+#include "content/browser/frame_host/frame_tree_node.h"
 #include "content/browser/frame_host/render_frame_host_impl.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/navigation_throttle.h"
@@ -154,6 +155,9 @@ class CONTENT_EXPORT NavigationHandleImpl : public NavigationHandle {
       scoped_refptr<net::HttpResponseHeaders> response_headers,
       const ThrottleChecksFinishedCallback& callback);
 
+  // Returns the FrameTreeNode this navigation is happening in.
+  FrameTreeNode* frame_tree_node() { return frame_tree_node_; }
+
   // Called when the navigation was redirected. This will update the |url_| and
   // inform the delegate.
   void DidRedirectNavigation(const GURL& new_url);