Selection API: document.open() should reset Selection.

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

 /*
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  * Copyright (C) 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 57 matching lines @@
 TreeScope::TreeScope(Document& document)
     : m_rootNode(document),
       m_document(&document),
       m_parentTreeScope(nullptr),
       m_idTargetObserverRegistry(IdTargetObserverRegistry::create()) {
   m_rootNode->setTreeScope(this);
 }
 
 TreeScope::~TreeScope() {}
 
+void TreeScope::resetTreeScope() {
+  m_selection = nullptr;
+}
+
 TreeScope* TreeScope::olderShadowRootOrParentTreeScope() const {
   if (rootNode().isShadowRoot()) {
     if (ShadowRoot* olderShadowRoot =
             toShadowRoot(rootNode()).olderShadowRoot())
       return olderShadowRoot;
   }
   return parentTreeScope();
 }
 
 bool TreeScope::isInclusiveOlderSiblingShadowRootOrAncestorTreeScopeOf(
@@ skipping 441 matching lines @@
   visitor->trace(m_idTargetObserverRegistry);
   visitor->trace(m_selection);
   visitor->trace(m_elementsById);
   visitor->trace(m_imageMapsByName);
   visitor->trace(m_scopedStyleResolver);
   visitor->trace(m_radioButtonGroupScope);
   visitor->trace(m_svgTreeScopedResources);
 }
 
 }  // namespace blink