Allow MimeHandlerViewGuest be embedded inside OOPIFs

content/browser/frame_host/render_widget_host_view_guest.h

Index: content/browser/frame_host/render_widget_host_view_guest.h
diff --git a/content/browser/frame_host/render_widget_host_view_guest.h b/content/browser/frame_host/render_widget_host_view_guest.h
index af8d734bb4e06f19661b45e7e651bcc4e94195c3..f0b1f4de2a026a6cbc1eebd74ce8cc22cabcdc9e 100644
--- a/content/browser/frame_host/render_widget_host_view_guest.h
+++ b/content/browser/frame_host/render_widget_host_view_guest.h
@@ -126,6 +126,7 @@ class CONTENT_EXPORT RenderWidgetHostViewGuest
                        InputEventAckState ack_result) override;
 
   bool IsRenderWidgetHostViewGuest() override;
+  RenderWidgetHostViewBase* GetOwnerRenderWidgetHostView() const;
 
  protected:
   friend class RenderWidgetHostView;
@@ -136,8 +137,6 @@ class CONTENT_EXPORT RenderWidgetHostViewGuest
       BrowserPluginGuest* guest,
       base::WeakPtr<RenderWidgetHostViewBase> platform_view);
 
-  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