Use C++11 features in core/html

Source/core/html/HTMLShadowElement.cpp

 /*
  * Copyright (C) 2012 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 37 matching lines @@
 DEFINE_NODE_FACTORY(HTMLShadowElement)
 
 HTMLShadowElement::~HTMLShadowElement()
 {
 }
 
 ShadowRoot* HTMLShadowElement::olderShadowRoot()
 {
     ShadowRoot* containingRoot = containingShadowRoot();
     if (!containingRoot)
-        return 0;
+        return nullptr;
 
     document().updateDistributionForNodeIfNeeded(this);
 
     ShadowRoot* older = containingRoot->olderShadowRoot();
     if (!older || !older->shouldExposeToBindings() || older->shadowInsertionPointOfYoungerShadowRoot() != this)
-        return 0;
+        return nullptr;
 
     ASSERT(older->shouldExposeToBindings());
     return older;
 }
 
 Node::InsertionNotificationRequest HTMLShadowElement::insertedInto(ContainerNode* insertionPoint)
 {
     if (insertionPoint->inDocument()) {
         // Warn if trying to reproject between user agent and author shadows.
         ShadowRoot* root = containingShadowRoot();
         if (root && root->olderShadowRoot() && root->type() != root->olderShadowRoot()->type()) {
             String message = String::format("<shadow> doesn't work for %s element host.", root->host()->tagName().utf8().data());
             document().addConsoleMessage(ConsoleMessage::create(RenderingMessageSource, WarningMessageLevel, message));
         }
     }
     return InsertionPoint::insertedInto(insertionPoint);
 }
 
 } // namespace blink