Make ElementShadow::youngestShadowRoot() return a reference

third_party/WebKit/Source/core/dom/shadow/ElementShadow.h

 /*
  * 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.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 29 matching lines @@
 namespace blink {
 
 class CORE_EXPORT ElementShadow final : public NoBaseWillBeGarbageCollectedFinalized<ElementShadow> {
     WTF_MAKE_NONCOPYABLE(ElementShadow);
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(ElementShadow);
 public:
     static PassOwnPtrWillBeRawPtr<ElementShadow> create();
     ~ElementShadow();
 
     Element* host() const;
-    ShadowRoot* youngestShadowRoot() const { return m_shadowRoots.head(); }
+    ShadowRoot& youngestShadowRoot() const { ASSERT(m_shadowRoots.head()); return *m_shadowRoots.head(); }
     ShadowRoot* oldestShadowRoot() const { return m_shadowRoots.tail(); }
     ElementShadow* containingShadow() const;
 
     ShadowRoot& addShadowRoot(Element& shadowHost, ShadowRootType);
 
     bool hasSameStyles(const ElementShadow*) const;
 
     void attach(const Node::AttachContext&);
     void detach(const Node::AttachContext&);
 
@@ skipping 38 matching lines @@
     SelectRuleFeatureSet m_selectFeatures;
     // FIXME: Oilpan: add a heap-based version of DoublyLinkedList<>.
     DoublyLinkedList<ShadowRoot> m_shadowRoots;
     bool m_needsDistributionRecalc;
     bool m_needsSelectFeatureSet;
 };
 
 inline Element* ElementShadow::host() const
 {
     ASSERT(!m_shadowRoots.isEmpty());
-    return youngestShadowRoot()->host();
+    return youngestShadowRoot().host();
 }
 
 inline ShadowRoot* Node::youngestShadowRoot() const
 {
     if (!isElementNode())
         return 0;
     return toElement(this)->youngestShadowRoot();
 }
 
 inline ShadowRoot* Element::youngestShadowRoot() const
 {
     if (ElementShadow* shadow = this->shadow())
-        return shadow->youngestShadowRoot();
+        return &shadow->youngestShadowRoot();
     return 0;
 }
 
 inline ElementShadow* ElementShadow::containingShadow() const
 {
     if (ShadowRoot* parentRoot = host()->containingShadowRoot())
         return parentRoot->owner();
     return 0;
 }
 
 inline void ElementShadow::distributeIfNeeded()
 {
     if (m_needsDistributionRecalc)
         distribute();
     m_needsDistributionRecalc = false;
 }
 
 } // namespace
 
 #endif