Only allow one shadowRoot.

sky/engine/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 13 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef SKY_ENGINE_CORE_DOM_SHADOW_ELEMENTSHADOW_H_
 #define SKY_ENGINE_CORE_DOM_SHADOW_ELEMENTSHADOW_H_
 
 #include "sky/engine/core/dom/shadow/InsertionPoint.h"
 #include "sky/engine/core/dom/shadow/SelectRuleFeatureSet.h"
 #include "sky/engine/core/dom/shadow/ShadowRoot.h"
 #include "sky/engine/platform/heap/Handle.h"
-#include "sky/engine/wtf/DoublyLinkedList.h"
 #include "sky/engine/wtf/HashMap.h"
 #include "sky/engine/wtf/Noncopyable.h"
 #include "sky/engine/wtf/PassOwnPtr.h"
 
 namespace blink {
 
 class ElementShadow final {
     WTF_MAKE_NONCOPYABLE(ElementShadow);
     WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<ElementShadow> create();
     ~ElementShadow();
 
     Element* host() const;
-    ShadowRoot* youngestShadowRoot() const { return m_shadowRoots.head(); }
-    ShadowRoot* oldestShadowRoot() const { return m_shadowRoots.tail(); }
+    ShadowRoot* shadowRoot() const { return m_shadowRoot; }
     ElementShadow* containingShadow() const;
 
     ShadowRoot& addShadowRoot(Element& shadowHost);
 
     bool hasSameStyles(const ElementShadow*) const;
 
     void attach(const Node::AttachContext&);
     void detach(const Node::AttachContext&);
 
     void willAffectSelector();
@@ skipping 20 matching lines @@
     void collectSelectFeatureSetFrom(ShadowRoot&);
     void distributeNodeChildrenTo(InsertionPoint*, ContainerNode*);
 
     bool needsSelectFeatureSet() const { return m_needsSelectFeatureSet; }
     void setNeedsSelectFeatureSet() { m_needsSelectFeatureSet = true; }
 
     typedef HashMap<RawPtr<const Node>, DestinationInsertionPoints> NodeToDestinationInsertionPoints;
     NodeToDestinationInsertionPoints m_nodeToInsertionPoints;
 
     SelectRuleFeatureSet m_selectFeatures;
-    // FIXME: Oilpan: add a heap-based version of DoublyLinkedList<>.
-    DoublyLinkedList<ShadowRoot> m_shadowRoots;
+    ShadowRoot* m_shadowRoot;
     bool m_needsDistributionRecalc;
     bool m_needsSelectFeatureSet;
 };
 
 inline Element* ElementShadow::host() const
 {
-    ASSERT(!m_shadowRoots.isEmpty());
-    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 0;
+    ASSERT(m_shadowRoot);
+    return m_shadowRoot->host();
 }
 
 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  // SKY_ENGINE_CORE_DOM_SHADOW_ELEMENTSHADOW_H_