RenderWidgetHostViewChildFrame's called a virtual in its ctor.

content/browser/frame_host/render_widget_host_view_guest.h

 // Copyright 2014 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_WIDGET_HOST_VIEW_GUEST_H_
 #define CONTENT_BROWSER_FRAME_HOST_RENDER_WIDGET_HOST_VIEW_GUEST_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 27 matching lines @@
 // content and therefore inherits from RenderWidgetHostViewChildFrame.
 // Eventually all RenderWidgetHostViewGuest code will be subsumed by
 // RenderWidgetHostViewChildFrame and this class will be removed.
 //
 // Some elements that are platform specific will be deal with by delegating
 // the relevant calls to the platform view.
 class CONTENT_EXPORT RenderWidgetHostViewGuest
     : public RenderWidgetHostViewChildFrame,
       public ui::GestureConsumer {
  public:
-  RenderWidgetHostViewGuest(
+  static RenderWidgetHostViewGuest* Create(
       RenderWidgetHost* widget,
       BrowserPluginGuest* guest,
       base::WeakPtr<RenderWidgetHostViewBase> platform_view);
   ~RenderWidgetHostViewGuest() override;
 
   bool OnMessageReceivedFromEmbedder(const IPC::Message& message,
                                      RenderWidgetHostImpl* embedder);
 
   // RenderWidgetHostView implementation.
   bool OnMessageReceived(const IPC::Message& msg) override;
@@ skipping 65 matching lines @@
                      InputEventAckState ack_result) override;
 
   void GestureEventAck(const blink::WebGestureEvent& event,
                        InputEventAckState ack_result) override;
 
   bool IsRenderWidgetHostViewGuest() override;
 
  protected:
   friend class RenderWidgetHostView;
 
+  RenderWidgetHostViewGuest(

[clamy, 2016/10/05 15:29:49]

It seems that no class inherits from RenderWidgetHostViewGuest. If so, can we
make its ctor private instead of protected?

[dtapuska, 2016/10/05 15:37:05]

Done.

+      RenderWidgetHost* widget,
+      BrowserPluginGuest* guest,
+      base::WeakPtr<RenderWidgetHostViewBase> platform_view);
+
  private:
   RenderWidgetHostViewBase* GetOwnerRenderWidgetHostView() const;
 
   // Since we now route GestureEvents directly to the guest renderer, we need
   // a way to make sure that the BrowserPlugin in the embedder gets focused so
   // that keyboard input (which still travels via BrowserPlugin) is routed to
   // the plugin and thus onwards to the guest.
   // TODO(wjmaclean): When we remove BrowserPlugin, delete this code.
   // http://crbug.com/533069
   void MaybeSendSyntheticTapGesture(
@@ skipping 11 matching lines @@
   // The platform view for this RenderWidgetHostView.
   // RenderWidgetHostViewGuest mostly only cares about stuff related to
   // compositing, the rest are directly forwarded to this |platform_view_|.
   base::WeakPtr<RenderWidgetHostViewBase> platform_view_;
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewGuest);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_RENDER_WIDGET_HOST_VIEW_GUEST_H_