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

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

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index e59fd92e24388367e640533f8a3d9c6eeb3d1eb2..cbe816ef8f9bf02befee98a13de80c9615995fa0 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -80,6 +80,7 @@
 #include "core/dom/ElementTraversal.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/ExecutionContextTask.h"
+#include "core/dom/FormElementObserver.h"
 #include "core/dom/FrameRequestCallback.h"
 #include "core/dom/IntersectionObserverController.h"
 #include "core/dom/LayoutTreeBuilderTraversal.h"
@@ -6740,6 +6741,7 @@ DEFINE_TRACE(Document) {
   visitor->Trace(resize_observer_controller_);
   visitor->Trace(property_registry_);
   visitor->Trace(network_state_observer_);
+  visitor->Trace(form_element_observer_);
   Supplementable<Document>::Trace(visitor);
   TreeScope::Trace(visitor);
   ContainerNode::Trace(visitor);
@@ -6763,6 +6765,12 @@ void Document::RecordDeferredLoadReason(WouldLoadReason reason) {
   would_load_reason_ = reason;
 }
 
+FormElementObserver* Document::GetFormElementObserver() {
+  if (!form_element_observer_)
+    form_element_observer_ = new FormElementObserver(*this);
+  return form_element_observer_;
+}
+
 DEFINE_TRACE_WRAPPERS(Document) {
   // node_lists_ are traced in their corresponding NodeListsNodeData, keeping
   // them only alive for live nodes. Otherwise we would keep lists of dead