Task Manager should listen to WebContentsObserver::RenderFrameCreated.

content/browser/frame_host/render_frame_host_impl.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_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 #define CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 154 matching lines @@
   void ActivateFindInPageResultForAccessibility(int request_id) override;
   void InsertVisualStateCallback(const VisualStateCallback& callback) override;
   void CopyImageAt(int x, int y) override;
   void SaveImageAt(int x, int y) override;
   RenderViewHost* GetRenderViewHost() override;
   service_manager::BinderRegistry* GetInterfaceRegistry() override;
   service_manager::InterfaceProvider* GetRemoteInterfaces() override;
   AssociatedInterfaceProvider* GetRemoteAssociatedInterfaces() override;
   blink::WebPageVisibilityState GetVisibilityState() override;
   bool IsRenderFrameLive() override;
+  bool IsCurrent() override;
   int GetProxyCount() override;
   void FilesSelectedInChooser(const std::vector<FileChooserFileInfo>& files,
                               FileChooserParams::Mode permissions) override;
   bool HasSelection() override;
   void RequestTextSurroundingSelection(
       const TextSurroundingSelectionCallback& callback,
       int max_length) override;
   void AllowBindings(int binding_flags) override;
   int GetEnabledBindings() const override;
   void BlockRequestsForFrame() override;
@@ skipping 1033 matching lines @@
 
   // NOTE: This must be the last member.
   base::WeakPtrFactory<RenderFrameHostImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_