Allow MimeHandlerViewGuest be embedded inside OOPIFs

content/public/browser/browser_plugin_guest_delegate.h

Index: content/public/browser/browser_plugin_guest_delegate.h
diff --git a/content/public/browser/browser_plugin_guest_delegate.h b/content/public/browser/browser_plugin_guest_delegate.h
index 0f805651ba8bafe5240a5fbe5772e06d43a75081..c6f3bc1cea88c4ddbefb762ede261dde7ed80508 100644
--- a/content/public/browser/browser_plugin_guest_delegate.h
+++ b/content/public/browser/browser_plugin_guest_delegate.h
@@ -97,6 +97,11 @@ class CONTENT_EXPORT BrowserPluginGuestDelegate {
   // a BrowserPlugin even when we are using cross process frames for guests. It
   // should be removed after resolving https://crbug.com/642826).
   virtual bool CanUseCrossProcessFrames();
+
+  // Returns the RenderFrameHost corresponding to the RenderFrame embedding the
+  // BrowserPlugin. This is the main frame for the owner of the guests, unless,
+  // the guest is embedded inside a cross origin frame.
+  virtual RenderFrameHost* GetEmbedderFrame();
 };
 
 }  // namespace content