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

components/autofill/content/renderer/password_autofill_agent.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_AUTOFILL_CONTENT_RENDERER_PASSWORD_AUTOFILL_AGENT_H_
 #define COMPONENTS_AUTOFILL_CONTENT_RENDERER_PASSWORD_AUTOFILL_AGENT_H_
 
 #include <map>
 #include <memory>
 #include <vector>
@@ skipping 129 matching lines @@
   // Called when the focused node has changed.
   void FocusedNodeHasChanged(const blink::WebNode& node);
 
   bool logging_state_active() const { return logging_state_active_; }
 
  protected:
   virtual bool OriginCanAccessPasswordManager(
       const blink::WebSecurityOrigin& origin);
 
  private:
+  class FormElementObserver;
+
   // Ways to restrict which passwords are saved in ProvisionallySavePassword.
   enum ProvisionallySaveRestriction {
     RESTRICTION_NONE,
     RESTRICTION_NON_EMPTY_PASSWORD
   };
 
   struct PasswordInfo {
     blink::WebInputElement password_field;
     PasswordFormFillData fill_data;
     // The user manually edited the password more recently than the username was
@@ skipping 141 matching lines @@
   // Contains server predictions for username, password and/or new password
   // fields for individual forms.
   FormsPredictionsMap form_predictions_;
 
   AutofillAgent* autofill_agent_;  // Weak reference.
 
   mojom::PasswordManagerDriverPtr password_manager_driver_;
 
   mojo::Binding<mojom::PasswordAutofillAgent> binding_;
 
+  FormElementObserver* form_element_observer_;  // Weak reference.
+
   DISALLOW_COPY_AND_ASSIGN(PasswordAutofillAgent);
 };
 
 }  // namespace autofill
 
 #endif  // COMPONENTS_AUTOFILL_CONTENT_RENDERER_PASSWORD_AUTOFILL_AGENT_H_