Use a weak pointer when binding GuestViewBase::DidAttach.

components/guest_view/browser/guest_view_message_filter.cc

Index: components/guest_view/browser/guest_view_message_filter.cc
diff --git a/components/guest_view/browser/guest_view_message_filter.cc b/components/guest_view/browser/guest_view_message_filter.cc
index 03aefe803a3c3b5b7eba3cde8fc6d3cfaf05885b..c2124ed258fc52d15093b9ea00dff28f8f4b5491 100644
--- a/components/guest_view/browser/guest_view_message_filter.cc
+++ b/components/guest_view/browser/guest_view_message_filter.cc
@@ -144,7 +144,8 @@ void GuestViewMessageFilter::OnAttachToEmbedderFrame(
 
   guest->WillAttach(
       owner_web_contents, element_instance_id, false,
-      base::Bind(&GuestViewMessageFilter::WillAttachCallback, this, guest));
+      base::Bind(&GuestViewBase::DidAttach,
+                 guest->weak_ptr_factory_.GetWeakPtr(), MSG_ROUTING_NONE));
 
   // Attach this inner WebContents |guest_web_contents| to the outer
   // WebContents |owner_web_contents|. The outer WebContents's
@@ -155,8 +156,4 @@ void GuestViewMessageFilter::OnAttachToEmbedderFrame(
                                                     embedder_frame);
 }
 
-void GuestViewMessageFilter::WillAttachCallback(GuestViewBase* guest) {
-  guest->DidAttach(MSG_ROUTING_NONE);
-}
-
 }  // namespace guest_view