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

third_party/WebKit/public/web/WebDocument.h

Index: third_party/WebKit/public/web/WebDocument.h
diff --git a/third_party/WebKit/public/web/WebDocument.h b/third_party/WebKit/public/web/WebDocument.h
index af9497b88337b948de03fb3dc6a995a22bfce308..e2657575187d659515efe4369d7eee1de717eaed 100644
--- a/third_party/WebKit/public/web/WebDocument.h
+++ b/third_party/WebKit/public/web/WebDocument.h
@@ -52,7 +52,9 @@ class Document;
 class WebAXObject;
 class WebElement;
 class WebFormElement;
+class WebFormElementObserverCallback;
 class WebElementCollection;
+class WebInputElement;
 class WebString;
 class WebURL;
 struct WebDistillabilityFeatures;
@@ -139,6 +141,18 @@ class WebDocument : public WebNode {
   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*);