Allow MimeHandlerViewGuest be embedded inside OOPIFs

extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h

Index: extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h
diff --git a/extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h b/extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h
index 87d249eb30ecdd268c56a8965caf04a362a2f36c..aa04f9cbf3d1e4f88e2998ef5257c591463f8d82 100644
--- a/extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h
+++ b/extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h
@@ -59,6 +59,9 @@ class MimeHandlerViewGuest :
   static const char Type[];
 
   bool CanUseCrossProcessFrames() override;
+  content::RenderFrameHost* GetEmbedderFrame() override;
+
+  void SetEmbedderFrame(int process_id, int routing_id);
 
  protected:
   explicit MimeHandlerViewGuest(content::WebContents* owner_web_contents);
@@ -100,6 +103,9 @@ class MimeHandlerViewGuest :
   std::unique_ptr<StreamContainer> stream_;
   std::string view_id_;
 
+  int embedder_frame_process_id_;
+  int embedder_frame_routing_id_;
+
   DISALLOW_COPY_AND_ASSIGN(MimeHandlerViewGuest);
 };