Support frame tree propagation between renderers in the same browsing instance.

content/browser/web_contents/render_view_host_manager.h

Index: content/browser/web_contents/render_view_host_manager.h
diff --git a/content/browser/web_contents/render_view_host_manager.h b/content/browser/web_contents/render_view_host_manager.h
index 9be59d31cceef814f8379acd63619ec7216fa038..a495b926401d61ea1f3dc7b9cf8118d497c397d7 100644
--- a/content/browser/web_contents/render_view_host_manager.h
+++ b/content/browser/web_contents/render_view_host_manager.h
@@ -162,6 +162,9 @@ class CONTENT_EXPORT RenderViewHostManager
   // Called when a renderer's main frame navigates.
   void DidNavigateMainFrame(content::RenderViewHost* render_view_host);
 
+  // Called when a renderer has navigated and its frame tree is updated.
+  void DidUpdateFrameTree(content::RenderViewHost* render_view_host);
+
   // Helper method to create a RenderViewHost.  If |swapped_out| is true, it
   // will be initially placed on the swapped out hosts list.  Otherwise, it
   // will be used for a pending cross-site navigation.