Utilize PassRefPtr and C++ refs in more places in ShadowRoot code

Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1710 matching lines @@
     if (ElementShadow* elementShadow = shadow()) {
         if (ShadowRoot* shadowRoot = elementShadow->oldestShadowRoot()) {
             ASSERT(shadowRoot->type() == ShadowRoot::UserAgentShadowRoot);
             return shadowRoot;
         }
     }
 
     return 0;
 }
 
-ShadowRoot* Element::ensureUserAgentShadowRoot()
+ShadowRoot& Element::ensureUserAgentShadowRoot()
 {
     if (ShadowRoot* shadowRoot = userAgentShadowRoot())
-        return shadowRoot;
-    ShadowRoot* shadowRoot = ensureShadow().addShadowRoot(*this, ShadowRoot::UserAgentShadowRoot);
-    didAddUserAgentShadowRoot(shadowRoot);
-    return shadowRoot;
+        return *shadowRoot;
+    RefPtr<ShadowRoot> shadowRoot = ensureShadow().addShadowRoot(*this, ShadowRoot::UserAgentShadowRoot);
+    didAddUserAgentShadowRoot(*shadowRoot);
+    return *shadowRoot;

[eseidel, 2013/11/06 01:11:17]

Who's holding onto this root... Lets hope didAddUserAgentShadowRoot does...
otherwise this looks crashy.

[adamk, 2013/11/06 02:01:39]

addShadowRoot does (ShadowRoot is TreeShared). What interface would you prefer
for this method?

 }
 
 bool Element::childTypeAllowed(NodeType type) const
 {
     switch (type) {
     case ELEMENT_NODE:
     case TEXT_NODE:
     case COMMENT_NODE:
     case PROCESSING_INSTRUCTION_NODE:
     case CDATA_SECTION_NODE:
@@ skipping 1735 matching lines @@
     // Before doing so, we need to resolve issues in HTMLSelectElement::recalcListItems
     // and RenderMenuList::setText. See also https://bugs.webkit.org/show_bug.cgi?id=88405
     if (hasTagName(optionTag) || hasTagName(optgroupTag))
         return false;
     if (FullscreenElementStack::isActiveFullScreenElement(this))
         return false;
     return true;
 }
 
 } // namespace WebCore