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

third_party/WebKit/public/web/modules/password_manager/WebFormElementObserverCallback.h

Index: third_party/WebKit/public/web/modules/password_manager/WebFormElementObserverCallback.h
diff --git a/third_party/WebKit/public/web/modules/password_manager/WebFormElementObserverCallback.h b/third_party/WebKit/public/web/modules/password_manager/WebFormElementObserverCallback.h
new file mode 100644
index 0000000000000000000000000000000000000000..9b8637c40e42832bd5552ff178023e2298fced06
--- /dev/null
+++ b/third_party/WebKit/public/web/modules/password_manager/WebFormElementObserverCallback.h
@@ -0,0 +1,21 @@
+// 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 WebFormElementObserverCallback_h
+#define WebFormElementObserverCallback_h
+
+namespace blink {
+
+class WebFormElementObserverCallback {
+ public:
+  virtual ~WebFormElementObserverCallback() {}
+
+  // Invoked when the observed element was either removed from the DOM, it's
+  // action attribute changed, or it's computed style changed to display: none.
+  virtual void ElementWasHiddenOrRemoved() = 0;
+};
+
+}  // namespace blink
+
+#endif  // WebFormElementObserverCallback_h