Allow MimeHandlerViewGuest be embedded inside OOPIFs

components/guest_view/browser/guest_view_base.cc

Index: components/guest_view/browser/guest_view_base.cc
diff --git a/components/guest_view/browser/guest_view_base.cc b/components/guest_view/browser/guest_view_base.cc
index e2ffccee70d4728e19726a3b7aea8f4c93c49aaa..63c9e05c425e63a657a5d78ba27b05a411bf62de 100644
--- a/components/guest_view/browser/guest_view_base.cc
+++ b/components/guest_view/browser/guest_view_base.cc
@@ -20,6 +20,7 @@
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
+#include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/page_zoom.h"
@@ -416,9 +417,9 @@ void GuestViewBase::DidAttach(int guest_proxy_routing_id) {
   DidAttachToEmbedder();
 
   // Inform the associated GuestViewContainer that the contentWindow is ready.
-  embedder_web_contents()->Send(new GuestViewMsg_GuestAttached(
-      element_instance_id_,
-      guest_proxy_routing_id));
+  GetEmbedderFrame()->GetView()->GetRenderWidgetHost()->Send(
+      new GuestViewMsg_GuestAttached(element_instance_id_,
+                                     guest_proxy_routing_id));
 
   SendQueuedEvents();
 }
@@ -726,6 +727,12 @@ void GuestViewBase::FindReply(WebContents* source,
   }
 }
 
+content::RenderFrameHost* GuestViewBase::GetEmbedderFrame() {
+  if (GetOwnerWebContents())
+    return GetOwnerWebContents()->GetMainFrame();
+  return nullptr;
+}
+
 void GuestViewBase::OnZoomChanged(
     const zoom::ZoomController::ZoomChangedEventData& data) {
   if (data.web_contents == embedder_web_contents()) {