Storage of ComputedStyle separate from LayoutObject.

third_party/WebKit/Source/core/dom/Node.h

Index: third_party/WebKit/Source/core/dom/Node.h
diff --git a/third_party/WebKit/Source/core/dom/Node.h b/third_party/WebKit/Source/core/dom/Node.h
index acd595fb9729ad9112a3489c70eeabbbe650027f..339b797de2209082d16267e0c08657da30baf1dd 100644
--- a/third_party/WebKit/Source/core/dom/Node.h
+++ b/third_party/WebKit/Source/core/dom/Node.h
@@ -90,7 +90,7 @@ class TagCollection;
 class Text;
 class TouchEvent;
 
-const int nodeStyleChangeShift = 19;
+const int nodeStyleChangeShift = 20;
 
 enum StyleChangeType {
     NoStyleChange = 0,
@@ -111,13 +111,17 @@ class NodeRareDataBase {
 public:
     LayoutObject* layoutObject() const { return m_layoutObject; }
     void setLayoutObject(LayoutObject* layoutObject) { m_layoutObject = layoutObject; }
+    ComputedStyle* computedStyle() const { return m_computedStyle; }
+    void setComputedStyle(ComputedStyle* computedStyle) { m_computedStyle = computedStyle; }
 
 protected:
     NodeRareDataBase(LayoutObject* layoutObject)
-        : m_layoutObject(layoutObject)
+        : m_computedStyle(nullptr)
+        , m_layoutObject(layoutObject)
     { }
 
 protected:
+    ComputedStyle* m_computedStyle;

[Timothy Loh, 2016/05/26 07:06:37]

This should be a RefPtr<ComputedStyle> and should probably be on NodeRareData
instead of NodeRareDataBase (afaict, this class exists only for inlining of the
layoutObject() function, see wkb.ug/100057 for context)

     // LayoutObjects are fully owned by their DOM node. See LayoutObject's
     // LIFETIME documentation section.
     LayoutObject* m_layoutObject;
@@ -516,14 +520,15 @@ public:
 
     // As layoutObject() includes a branch you should avoid calling it repeatedly in hot code paths.
     // Note that if a Node has a layoutObject, it's parentNode is guaranteed to have one as well.
-    LayoutObject* layoutObject() const { return hasRareData() ? m_data.m_rareData->layoutObject() : m_data.m_layoutObject; }
-    void setLayoutObject(LayoutObject* layoutObject)
+    LayoutObject* layoutObject() const
     {
         if (hasRareData())
-            m_data.m_rareData->setLayoutObject(layoutObject);
+            return m_data.m_rareData->layoutObject();
         else
-            m_data.m_layoutObject = layoutObject;
+            return hasLayoutObject() ? m_data.m_layoutObject : nullptr;
     }
+    void setLayoutObject(LayoutObject*);
+    void clearStyleAndLayoutObject();
 
     // Use these two methods with caution.
     LayoutBox* layoutBox() const;
@@ -556,6 +561,7 @@ public:
     // Wrapper for nodes that don't have a layoutObject, but still cache the style (like HTMLOptionElement).
     ComputedStyle* mutableComputedStyle() const;
     const ComputedStyle* computedStyle() const;
+    void setComputedStyle(ComputedStyle*);
     const ComputedStyle* parentComputedStyle() const;
 
     const ComputedStyle& computedStyleRef() const;
@@ -689,49 +695,50 @@ public:
 
 private:
     enum NodeFlags {
-        HasRareDataFlag = 1,
+        HasLayoutObjectFlag = 1,
+        HasRareDataFlag = 1 << 1,
 
         // Node type flags. These never change once created.
-        IsTextFlag = 1 << 1,
-        IsContainerFlag = 1 << 2,
-        IsElementFlag = 1 << 3,
-        IsHTMLFlag = 1 << 4,
-        IsSVGFlag = 1 << 5,
-        IsDocumentFragmentFlag = 1 << 6,
-        IsInsertionPointFlag = 1 << 7,
+        IsTextFlag = 1 << 2,
+        IsContainerFlag = 1 << 3,
+        IsElementFlag = 1 << 4,
+        IsHTMLFlag = 1 << 5,
+        IsSVGFlag = 1 << 6,
+        IsDocumentFragmentFlag = 1 << 7,
+        IsInsertionPointFlag = 1 << 8,
 
         // Changes based on if the element should be treated like a link,
         // ex. When setting the href attribute on an <a>.
-        IsLinkFlag = 1 << 8,
+        IsLinkFlag = 1 << 9,
 
         // Changes based on :hover, :active and :focus state.
-        IsUserActionElementFlag = 1 << 9,
+        IsUserActionElementFlag = 1 << 10,
 
         // Tree state flags. These change when the element is added/removed
         // from a DOM tree.
-        InDocumentFlag = 1 << 10,
-        IsInShadowTreeFlag = 1 << 11,
+        InDocumentFlag = 1 << 11,
+        IsInShadowTreeFlag = 1 << 12,
 
         // Set by the parser when the children are done parsing.
-        IsFinishedParsingChildrenFlag = 1 << 12,
+        IsFinishedParsingChildrenFlag = 1 << 13,
 
         // Flags related to recalcStyle.
-        SVGFilterNeedsLayerUpdateFlag = 1 << 13,
-        HasCustomStyleCallbacksFlag = 1 << 14,
-        ChildNeedsStyleInvalidationFlag = 1 << 15,
-        NeedsStyleInvalidationFlag = 1 << 16,
-        ChildNeedsDistributionRecalcFlag = 1 << 17,
-        ChildNeedsStyleRecalcFlag = 1 << 18,
+        SVGFilterNeedsLayerUpdateFlag = 1 << 14,
+        HasCustomStyleCallbacksFlag = 1 << 15,
+        ChildNeedsStyleInvalidationFlag = 1 << 16,
+        NeedsStyleInvalidationFlag = 1 << 17,
+        ChildNeedsDistributionRecalcFlag = 1 << 18,
+        ChildNeedsStyleRecalcFlag = 1 << 19,
         StyleChangeMask = 1 << nodeStyleChangeShift | 1 << (nodeStyleChangeShift + 1),
 
-        CustomElementFlag = 1 << 21,
-        CustomElementCustomFlag = 1 << 22,
+        CustomElementFlag = 1 << 22,
+        CustomElementCustomFlag = 1 << 23,
 
-        HasNameOrIsEditingTextFlag = 1 << 23,
-        HasWeakReferencesFlag = 1 << 24,
-        V8CollectableDuringMinorGCFlag = 1 << 25,
-        HasEventTargetDataFlag = 1 << 26,
-        AlreadySpellCheckedFlag = 1 << 27,
+        HasNameOrIsEditingTextFlag = 1 << 24,
+        HasWeakReferencesFlag = 1 << 25,
+        V8CollectableDuringMinorGCFlag = 1 << 26,
+        HasEventTargetDataFlag = 1 << 27,
+        AlreadySpellCheckedFlag = 1 << 28,
 
         V0CustomElementFlag = 1 << 28,
         V0CustomElementUpgradedFlag = 1 << 29,
@@ -771,6 +778,7 @@ protected:
 
     static void reattachWhitespaceSiblingsIfNeeded(Text* start);
 
+    bool hasLayoutObject() const { return getFlag(HasLayoutObjectFlag); }
     bool hasRareData() const { return getFlag(HasRareDataFlag); }
 
     NodeRareData* rareData() const;
@@ -826,7 +834,8 @@ private:
     Member<Node> m_next;
     // When a node has rare data we move the layoutObject into the rare data.
     union DataUnion {
-        DataUnion() : m_layoutObject(nullptr) { }
+        DataUnion() : m_computedStyle(nullptr) { }
+        ComputedStyle* m_computedStyle;

[Timothy Loh, 2016/05/26 07:06:37]

This probably needs lifetime management (i.e. refs and derefs when
setting/clearing). The finalizer should probably also check that we don't have a
computed style.

         // LayoutObjects are fully owned by their DOM node. See LayoutObject's
         // LIFETIME documentation section.
         LayoutObject* m_layoutObject;