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

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 90 matching lines @@
 class ElementRegistrationOptions;
 class Event;
 class EventFactoryBase;
 class EventListener;
 template <typename EventType>
 class EventWithHitTestResults;
 class ExceptionState;
 class FloatQuad;
 class FloatRect;
 class FormController;
+class FormElementObserver;
 class FrameRequestCallback;
 class FrameView;
 class HTMLAllCollection;
 class HTMLBodyElement;
 class HTMLCollection;
 class HTMLDialogElement;
 class HTMLElement;
 class HTMLFrameOwnerElement;
 class HTMLHeadElement;
 class HTMLImportLoader;
@@ skipping 1192 matching lines @@
   PropertyRegistry* GetPropertyRegistry();
 
   // Document maintains a counter of visible non-secure password
   // fields in the page. Used to notify the embedder when all visible
   // non-secure passwords fields are no longer visible.
   void IncrementPasswordCount();
   void DecrementPasswordCount();
 
   CoreProbeSink* GetProbeSink() final;
 
+  FormElementObserver* GetFormElementObserver();
+
  protected:
   Document(const DocumentInit&, DocumentClassFlags = kDefaultDocumentClass);
 
   void DidUpdateSecurityOrigin() final;
 
   void ClearXMLVersion() { xml_version_ = String(); }
 
   virtual Document* CloneDocumentWithoutChildren();
 
   bool ImportContainerNodeChildren(ContainerNode* old_container_node,
@@ skipping 347 matching lines @@
 
   Member<PropertyRegistry> property_registry_;
 
   unsigned password_count_;
 
   TaskHandle sensitive_input_visibility_task_;
 
   mojom::EngagementLevel engagement_level_;
 
   Member<NetworkStateObserver> network_state_observer_;
+
+  Member<FormElementObserver> form_element_observer_;

[dglazkov, 2017/05/11 21:09:05]

Does it have to be a member of Document? I am primarily worried about adding
things to Document that aren't technically part of core DOM implementation.

It looks like it's instantiated on access (RAII pattern), so maybe it could be
in a separate class? IOW, could we introduce WebFormElementObserver, which wraps
the observer and then let create it in PasswordAutofillAgent, passing
WebDocument to it?

 };
 
 extern template class CORE_EXTERN_TEMPLATE_EXPORT Supplement<Document>;
 
 inline bool Document::ShouldOverrideLegacyDescription(
     ViewportDescription::Type origin) const {
   // The different (legacy) meta tags have different priorities based on the
   // type regardless of which order they appear in the DOM. The priority is
   // given by the ViewportDescription::Type enum.
   return origin >= legacy_viewport_description_.type;
@@ skipping 34 matching lines @@
 DEFINE_TYPE_CASTS(TreeScope, Document, document, true, true);
 
 }  // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 CORE_EXPORT void showLiveDocumentInstances();
 #endif
 
 #endif  // Document_h