Allow MimeHandlerViewGuest be embedded inside OOPIFs

content/public/browser/guest_host.h

Index: content/public/browser/guest_host.h
diff --git a/content/public/browser/guest_host.h b/content/public/browser/guest_host.h
index a1b429f535b9251e5121b254053eab2d2580f96c..f2baf8f01ed3ba69a7f0d6d01521da7ce2fc5861 100644
--- a/content/public/browser/guest_host.h
+++ b/content/public/browser/guest_host.h
@@ -9,6 +9,8 @@
 
 namespace content {
 
+class WebContents;
+
 // A GuestHost is the content API for a guest WebContents.
 // Guests are top-level frames that can be embedded within other pages.
 // The content module manages routing of input events and compositing, but all
@@ -33,6 +35,10 @@ class GuestHost {
 
   // Called when the GuestHost is about to be destroyed.
   virtual void WillDestroy() = 0;
+
+  // Registers the |process_id| and |routing_id| of the embedder frame for this
+  // guest and returns the WebContents associated with the frame.
+  virtual WebContents* RegisterEmbedderID(int process_id, int routing_id) = 0;
 };
 
 }  // namespace content