Add DocumentShutdown{Notifier,Observer}

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

 /*
  * 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, 2011, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
@@ skipping 2621 matching lines @@
         cache->Remove(&node);
       }
     }
   }
 
   GetStyleEngine().DidDetach();
 
   GetPage()->GetEventHandlerRegistry().DocumentDetached(*this);
 
   // Signal destruction to mutation observers.
+  DocumentShutdownNotifier::NotifyContextDestroyed();
   SynchronousMutationNotifier::NotifyContextDestroyed();
 
   // If this Document is associated with a live DocumentLoader, the
   // DocumentLoader will take care of clearing the FetchContext. Deferring
   // to the DocumentLoader when possible also prevents prematurely clearing
   // the context in the case where multiple Documents end up associated with
   // a single DocumentLoader (e.g., navigating to a javascript: url).
   if (!Loader())
     fetcher_->ClearContext();
   // If this document is the master for an HTMLImportsController, sever that
@@ skipping 4199 matching lines @@
   visitor->Trace(intersection_observer_controller_);
   visitor->Trace(snap_coordinator_);
   visitor->Trace(resize_observer_controller_);
   visitor->Trace(property_registry_);
   visitor->Trace(network_state_observer_);
   Supplementable<Document>::Trace(visitor);
   TreeScope::Trace(visitor);
   ContainerNode::Trace(visitor);
   ExecutionContext::Trace(visitor);
   SecurityContext::Trace(visitor);
+  DocumentShutdownNotifier::Trace(visitor);
   SynchronousMutationNotifier::Trace(visitor);
 }
 
 void Document::RecordDeferredLoadReason(WouldLoadReason reason) {
   DCHECK(would_load_reason_ == WouldLoadReason::kInvalid ||
          reason != WouldLoadReason::kCreated);
   DCHECK(reason != WouldLoadReason::kInvalid);
   DCHECK(GetFrame());
   DCHECK(GetFrame()->IsCrossOriginSubframe());
   if (reason <= would_load_reason_ ||
@@ skipping 32 matching lines @@
 }
 
 void showLiveDocumentInstances() {
   WeakDocumentSet& set = liveDocumentSet();
   fprintf(stderr, "There are %u documents currently alive:\n", set.size());
   for (blink::Document* document : set)
     fprintf(stderr, "- Document %p URL: %s\n", document,
             document->Url().GetString().Utf8().data());
 }
 #endif