Use an MutationObserver to check when a password form disappears after XHR

components/autofill/content/renderer/password_autofill_agent.h

Index: components/autofill/content/renderer/password_autofill_agent.h
diff --git a/components/autofill/content/renderer/password_autofill_agent.h b/components/autofill/content/renderer/password_autofill_agent.h
index b8f80e7f3807e64e90c32cc3fe552f6ac1fa63d0..2caeb60761fff69d5947c6da101440a9cb2913a5 100644
--- a/components/autofill/content/renderer/password_autofill_agent.h
+++ b/components/autofill/content/renderer/password_autofill_agent.h
@@ -26,6 +26,7 @@
 #include "third_party/WebKit/public/web/WebInputElement.h"
 
 namespace blink {
+class WebFormElementObserver;
 class WebInputElement;
 class WebSecurityOrigin;
 }
@@ -147,6 +148,8 @@ class PasswordAutofillAgent : public content::RenderFrameObserver,
       const blink::WebSecurityOrigin& origin);
 
  private:
+  class FormElementObserverCallback;
+
   // Ways to restrict which passwords are saved in ProvisionallySavePassword.
   enum ProvisionallySaveRestriction {
     RESTRICTION_NONE,
@@ -258,7 +261,8 @@ class PasswordAutofillAgent : public content::RenderFrameObserver,
                                  ProvisionallySaveRestriction restriction);
 
   // Helper function called when same-document navigation completed
-  void OnSameDocumentNavigationCompleted(bool is_inpage_navigation);
+  void OnSameDocumentNavigationCompleted(
+      PasswordForm::SubmissionIndicatorEvent event);
 
   const mojom::AutofillDriverPtr& GetAutofillDriver();
 
@@ -308,6 +312,8 @@ class PasswordAutofillAgent : public content::RenderFrameObserver,
 
   mojo::Binding<mojom::PasswordAutofillAgent> binding_;
 
+  blink::WebFormElementObserver* form_element_observer_;
+
   DISALLOW_COPY_AND_ASSIGN(PasswordAutofillAgent);
 };