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 10c0ad42c875e04138ef7830f1e47ac08bd12540..aacf7ad1b538a582405f035ecc793efb00defc86 100644
--- a/content/browser/frame_host/render_widget_host_view_guest.h
+++ b/content/browser/frame_host/render_widget_host_view_guest.h
@@ -127,6 +127,7 @@ class CONTENT_EXPORT RenderWidgetHostViewGuest
                        InputEventAckState ack_result) override;
 
   bool IsRenderWidgetHostViewGuest() override;
+  RenderWidgetHostViewBase* GetOwnerRenderWidgetHostView() const override;
 
  protected:
   friend class RenderWidgetHostView;
@@ -137,8 +138,6 @@ 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