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

components/autofill/content/renderer/provisionally_saved_password_form.h

 // Copyright 2017 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_PROVISIONALLY_SAVED_PASSWORD_FORM_H_
 #define COMPONENTS_AUTOFILL_CONTENT_RENDERER_PROVISIONALLY_SAVED_PASSWORD_FORM_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 20 matching lines @@
   // password data may be invalid (e.g. empty username or password).
   bool IsSet() const;
   // Returns true if |password_form_| has enough information that it is likely
   // filled out.
   bool IsPasswordValid() const;
 
   const PasswordForm& password_form() const {
     DCHECK(IsSet());
     return *password_form_;
   }
-  const blink::WebFormElement& form_element() const { return form_element_; }
-  const blink::WebInputElement& input_element() const { return input_element_; }
+  blink::WebFormElement& form_element() { return form_element_; }
+  blink::WebInputElement& input_element() { return input_element_; }
 
  private:
   std::unique_ptr<PasswordForm> password_form_;
   // Last used WebFormElement for the PasswordForm submission. Can be null if
   // the form is unowned.
   blink::WebFormElement form_element_;
   // Last used WebInputElement which led to the PasswordForm update. Can be null
   // if the user has performed a form submission (via a button, for example).
   blink::WebInputElement input_element_;
 
   DISALLOW_COPY_AND_ASSIGN(ProvisionallySavedPasswordForm);
 };
 
 }  // namespace autofill
 
 #endif  // COMPONENTS_AUTOFILL_CONTENT_RENDERER_PROVISIONALLY_SAVED_PASSWORD_FORM_H_