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

third_party/WebKit/public/web/WebDocument.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 34 matching lines @@
 template <class T>
 class Local;
 }
 
 namespace blink {
 
 class Document;
 class WebAXObject;
 class WebElement;
 class WebFormElement;
+class WebFormElementObserverCallback;
 class WebElementCollection;
+class WebInputElement;
 class WebString;
 class WebURL;
 struct WebDistillabilityFeatures;
 
 // Provides readonly access to some properties of a DOM document.
 class WebDocument : public WebNode {
  public:
   WebDocument() {}
   WebDocument(const WebDocument& e) : WebNode(e) {}
 
@@ skipping 66 matching lines @@
 
   BLINK_EXPORT v8::Local<v8::Value> RegisterEmbedderCustomElement(
       const WebString& name,
       v8::Local<v8::Value> options,
       WebExceptionCode&);
 
   BLINK_EXPORT WebURL ManifestURL() const;
   BLINK_EXPORT bool ManifestUseCredentials() const;
   BLINK_EXPORT WebDistillabilityFeatures DistillabilityFeatures();
 
+  // Autofill support.
+
+  // Invoke callback once the passed form or input element is either removed
+  // from the DOM tree, or its  display class is set to none. Ownership
+  // of the callback is taken by the WebDocument.
+  BLINK_EXPORT void ObserveFormElement(
+      WebFormElement&,
+      std::unique_ptr<WebFormElementObserverCallback>);
+  BLINK_EXPORT void ObserveFormElement(
+      WebInputElement&,
+      std::unique_ptr<WebFormElementObserverCallback>);
+
 #if BLINK_IMPLEMENTATION
   BLINK_EXPORT WebDocument(Document*);
   BLINK_EXPORT WebDocument& operator=(Document*);
   BLINK_EXPORT operator Document*() const;
 #endif
 };
 
 DECLARE_WEB_NODE_TYPE_CASTS(WebDocument);
 
 }  // namespace blink
 
 #endif