HTMLPortalElement::DisconnectContentFrame and RemovedFrom redundantly clear the portal remote.

Do it in the former (which runs earlier) and merely DCHECK in the latter.

Change-Id: I53c0a8a64ec4f2b909de6dd710167d3f8e8aefac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1769522Reviewed-by: Lucas Gadani <lfg@chromium.org>
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690160}

third_party/blink/renderer/core/html/portal/html_portal_element.cc

@@ -378,13 +378,8 @@ HTMLPortalElement::InsertionNotificationRequest HTMLPortalElement::InsertedInto(
 }
 
 void HTMLPortalElement::RemovedFrom(ContainerNode& node) {
+  DCHECK(!remote_portal_.is_bound());
   HTMLFrameOwnerElement::RemovedFrom(node);
-
-  Document& document = GetDocument();
-
-  if (node.IsInDocumentTree() && document.IsHTMLDocument()) {
-    ConsumePortal();
-  }
 }
 
 bool HTMLPortalElement::IsURLAttribute(const Attribute& attribute) const {