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

third_party/WebKit/Source/core/dom/FormElementObserver.h

Index: third_party/WebKit/Source/core/dom/FormElementObserver.h
diff --git a/third_party/WebKit/Source/core/dom/FormElementObserver.h b/third_party/WebKit/Source/core/dom/FormElementObserver.h
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index 0000000000000000000000000000000000000000..d9d14ec288e40a9a089eb4a59f8aff3df5e4b05b
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+++ b/third_party/WebKit/Source/core/dom/FormElementObserver.h
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+// 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 FormElementObserver_h
+#define FormElementObserver_h
+
+#include "core/CoreExport.h"
+#include "platform/heap/HeapAllocator.h"
+#include "platform/heap/Member.h"
+
+namespace blink {
+
+class Document;
+class HTMLElement;
+class HTMLFormElement;
+class HTMLInputElement;
+class MutationObserver;
+class WebFormElementObserverCallback;
+
+class CORE_EXPORT FormElementObserver final
+    : public GarbageCollectedFinalized<FormElementObserver> {
+  WTF_MAKE_NONCOPYABLE(FormElementObserver);
+
+ public:
+  explicit FormElementObserver(Document&);
+  ~FormElementObserver();
+
+  void Observe(HTMLFormElement&,
+               std::unique_ptr<WebFormElementObserverCallback>);
+  void Observe(HTMLInputElement&,
+               std::unique_ptr<WebFormElementObserverCallback>);
+
+  DECLARE_VIRTUAL_TRACE();
+
+ private:
+  class ObserverCallback;
+
+  void EnsureObserver();
+  void ClearObserver();
+  void ObserveInternal(HTMLElement&,
+                       std::unique_ptr<WebFormElementObserverCallback>);
+  void NotifyMutation(HTMLElement&);
+
+  Member<Document> document_;
+  Member<ObserverCallback> callback_;
+  Member<MutationObserver> mutation_observer_;
+  HeapHashMap<Member<HTMLElement>,
+              std::unique_ptr<WebFormElementObserverCallback>>
+      callbacks_;
+};
+
+}  // namespace blink
+
+#endif  // FormElementObserver_h