Reduce a shadow root object's size by not inheriting DoublyLinkedList

third_party/WebKit/Source/core/dom/shadow/ShadowRoot.cpp

 /*
  * Copyright (C) 2011 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 25 matching lines @@
 #include "core/dom/shadow/ElementShadow.h"
 #include "core/dom/shadow/InsertionPoint.h"
 #include "core/dom/shadow/ShadowRootRareData.h"
 #include "core/dom/shadow/ShadowRootRareDataV0.h"
 #include "core/editing/serializers/Serialization.h"
 #include "core/html/HTMLShadowElement.h"
 #include "public/platform/Platform.h"
 
 namespace blink {
 
-struct SameSizeAsShadowRoot : public DocumentFragment, public TreeScope, public DoublyLinkedListNode<ShadowRoot> {
+struct SameSizeAsShadowRoot : public DocumentFragment, public TreeScope {
     char emptyClassFieldsDueToGCMixinMarker[1];
-    Member<void*> willbeMember[5];
+    Member<void*> willbeMember[3];
     unsigned countersAndFlags[1];
 };
 
 static_assert(sizeof(ShadowRoot) == sizeof(SameSizeAsShadowRoot), "ShadowRoot should stay small");
 
 ShadowRoot::ShadowRoot(Document& document, ShadowRootType type)
     : DocumentFragment(0, CreateShadowRoot)
     , TreeScope(*this, document)
-    , m_prev(nullptr)
-    , m_next(nullptr)
-    , m_slotAssignment(nullptr)
     , m_numberOfStyles(0)
     , m_type(static_cast<unsigned>(type))
     , m_registeredWithParentShadowRoot(false)
     , m_descendantInsertionPointsIsValid(false)
     , m_delegatesFocus(false)
     , m_descendantSlotsIsValid(false)
 {
 }
 
 ShadowRoot::~ShadowRoot()
 {
 }
 
+ShadowRoot* ShadowRoot::youngerShadowRoot() const
+{
+    if (type() == ShadowRootType::V0 && m_shadowRootRareDataV0)
+        return m_shadowRootRareDataV0->youngerShadowRoot();
+    return nullptr;
+}
+
+ShadowRoot* ShadowRoot::olderShadowRoot() const
+{
+    if (type() == ShadowRootType::V0 && m_shadowRootRareDataV0)
+        return m_shadowRootRareDataV0->olderShadowRoot();
+    return nullptr;
+}
+
 ShadowRoot* ShadowRoot::olderShadowRootForBindings() const
 {
     ShadowRoot* older = olderShadowRoot();
     while (older && !older->isOpenOrV0())
         older = older->olderShadowRoot();
     DCHECK(!older || older->isOpenOrV0());
     return older;
 }
 
+void ShadowRoot::setYoungerShadowRoot(ShadowRoot& root)
+{
+    DCHECK_EQ(type(), ShadowRootType::V0);
+    ensureShadowRootRareDataV0().setYoungerShadowRoot(root);
+}
+
+void ShadowRoot::setOlderShadowRoot(ShadowRoot& root)
+{
+    DCHECK_EQ(type(), ShadowRootType::V0);
+    ensureShadowRootRareDataV0().setOlderShadowRoot(root);
+}
+
 Node* ShadowRoot::cloneNode(bool, ExceptionState& exceptionState)
 {
     exceptionState.throwDOMException(NotSupportedError, "ShadowRoot nodes are not clonable.");
     return nullptr;
 }
 
 String ShadowRoot::innerHTML() const
 {
     return createMarkup(this, ChildrenOnly);
 }
@@ skipping 87 matching lines @@
 {
     ++m_numberOfStyles;
 }
 
 void ShadowRoot::unregisterScopedHTMLStyleChild()
 {
     DCHECK_GT(m_numberOfStyles, 0u);
     --m_numberOfStyles;
 }
 
-ShadowRootRareData* ShadowRoot::ensureShadowRootRareData()
+ShadowRootRareData& ShadowRoot::ensureShadowRootRareData()
 {
     if (m_shadowRootRareData)
-        return m_shadowRootRareData.get();
+        return *m_shadowRootRareData;
 
     m_shadowRootRareData = new ShadowRootRareData;
-    return m_shadowRootRareData.get();
+    return *m_shadowRootRareData;
 }
 
-ShadowRootRareDataV0* ShadowRoot::ensureShadowRootRareDataV0()
+ShadowRootRareDataV0& ShadowRoot::ensureShadowRootRareDataV0()
 {
     if (m_shadowRootRareDataV0)
-        return m_shadowRootRareDataV0.get();
+        return *m_shadowRootRareDataV0;
 
     m_shadowRootRareDataV0 = new ShadowRootRareDataV0;
-    return m_shadowRootRareDataV0.get();
+    return *m_shadowRootRareDataV0;
 }
 
 bool ShadowRoot::containsShadowElements() const
 {
     return m_shadowRootRareDataV0 ? m_shadowRootRareDataV0->containsShadowElements() : false;
 }
 
 bool ShadowRoot::containsContentElements() const
 {
     return m_shadowRootRareDataV0 ? m_shadowRootRareDataV0->containsContentElements() : false;
@@ skipping 11 matching lines @@
 
 HTMLShadowElement* ShadowRoot::shadowInsertionPointOfYoungerShadowRoot() const
 {
     return m_shadowRootRareDataV0 ? m_shadowRootRareDataV0->shadowInsertionPointOfYoungerShadowRoot() : nullptr;
 }
 
 void ShadowRoot::setShadowInsertionPointOfYoungerShadowRoot(HTMLShadowElement* shadowInsertionPoint)
 {
     if (!m_shadowRootRareDataV0 && !shadowInsertionPoint)
         return;
-    ensureShadowRootRareDataV0()->setShadowInsertionPointOfYoungerShadowRoot(shadowInsertionPoint);
+    ensureShadowRootRareDataV0().setShadowInsertionPointOfYoungerShadowRoot(shadowInsertionPoint);
 }
 
 void ShadowRoot::didAddInsertionPoint(InsertionPoint* insertionPoint)
 {
-    ensureShadowRootRareDataV0()->didAddInsertionPoint(insertionPoint);
+    ensureShadowRootRareDataV0().didAddInsertionPoint(insertionPoint);
     invalidateDescendantInsertionPoints();
 }
 
 void ShadowRoot::didRemoveInsertionPoint(InsertionPoint* insertionPoint)
 {
     m_shadowRootRareDataV0->didRemoveInsertionPoint(insertionPoint);
     invalidateDescendantInsertionPoints();
 }
 
 void ShadowRoot::addChildShadowRoot()
 {
-    ensureShadowRootRareData()->didAddChildShadowRoot();
+    ensureShadowRootRareData().didAddChildShadowRoot();
 }
 
 void ShadowRoot::removeChildShadowRoot()
 {
     // FIXME: Why isn't this an ASSERT?
     if (!m_shadowRootRareData)
         return;
     m_shadowRootRareData->didRemoveChildShadowRoot();
 }
 
@@ skipping 16 matching lines @@
 
     m_descendantInsertionPointsIsValid = true;
 
     if (!containsInsertionPoints())
         return emptyList;
 
     HeapVector<Member<InsertionPoint>> insertionPoints;
     for (InsertionPoint& insertionPoint : Traversal<InsertionPoint>::descendantsOf(*this))
         insertionPoints.append(&insertionPoint);
 
-    ensureShadowRootRareDataV0()->setDescendantInsertionPoints(insertionPoints);
+    ensureShadowRootRareDataV0().setDescendantInsertionPoints(insertionPoints);
 
     return m_shadowRootRareDataV0->descendantInsertionPoints();
 }
 
 StyleSheetList* ShadowRoot::styleSheets()
 {
-    if (!ensureShadowRootRareData()->styleSheets())
+    if (!ensureShadowRootRareData().styleSheets())
         m_shadowRootRareData->setStyleSheets(StyleSheetList::create(this));
 
     return m_shadowRootRareData->styleSheets();
 }
 
 void ShadowRoot::didAddSlot()
 {
-    ensureShadowRootRareData()->didAddSlot();
+    ensureShadowRootRareData().didAddSlot();
     invalidateDescendantSlots();
 }
 
 void ShadowRoot::didRemoveSlot()
 {
     DCHECK(m_shadowRootRareData);
     m_shadowRootRareData->didRemoveSlot();
     invalidateDescendantSlots();
 }
 
@@ skipping 30 matching lines @@
 
 void ShadowRoot::distributeV1()
 {
     if (!m_slotAssignment)
         m_slotAssignment = SlotAssignment::create();
     m_slotAssignment->resolveAssignment(*this);
 }
 
 DEFINE_TRACE(ShadowRoot)
 {
-    visitor->trace(m_prev);
-    visitor->trace(m_next);
     visitor->trace(m_shadowRootRareData);
     visitor->trace(m_shadowRootRareDataV0);
     visitor->trace(m_slotAssignment);
     TreeScope::trace(visitor);
     DocumentFragment::trace(visitor);
 }
 
 std::ostream& operator<<(std::ostream& ostream, const ShadowRootType& type)
 {
     switch (type) {
     case ShadowRootType::UserAgent:
         ostream << "ShadowRootType::UserAgent";
         break;
     case ShadowRootType::V0:
         ostream << "ShadowRootType::V0";
         break;
     case ShadowRootType::Open:
         ostream << "ShadowRootType::Open";
         break;
     case ShadowRootType::Closed:
         ostream << "ShadowRootType::Closed";
         break;
     }
     return ostream;
 }
 
 } // namespace blink