Improve positioned/percentHeight descendant/container tracking

third_party/WebKit/Source/core/layout/LayoutBox.h

Index: third_party/WebKit/Source/core/layout/LayoutBox.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutBox.h b/third_party/WebKit/Source/core/layout/LayoutBox.h
index 31aefb616e45aebfedcc0c7e5271334ffa4c2b1a..f5c0726e7c4f0c32e13f3f6df3e4e253bf356cd7 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.h
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.h
@@ -58,8 +58,11 @@ public:
         , m_overrideLogicalContentHeight(-1)
         , m_overrideLogicalContentWidth(-1)
         , m_previousBorderBoxSize(-1, -1)
+        , m_positionedContainer(nullptr)
+        , m_percentHeightContainer(nullptr)
     {
     }
+    virtual ~LayoutBoxRareData() { }

[esprehn, 2016/01/06 19:37:25]

we make this non-virtual in ElementRareData/NodeRareData and make it the
responsibility of the owner to destroy it at the correct type which saves 1 ptr
(the vtable) for every rare data.

[Xianzhu, 2016/01/06 20:49:07]

Done.

 
     // For inline replaced elements, the inline box that owns us.
     InlineBox* m_inlineBoxWrapper;
@@ -78,6 +81,11 @@ public:
     LayoutUnit m_pageLogicalOffset;
 
     LayoutUnit m_paginationStrut;
+
+    // Points to the LayoutBlock whose LayoutBlockRareData::m_positionedDescendants contains this LayoutBox.
+    LayoutBlock* m_positionedContainer;
+    // Points to the LayoutBlock whose LayoutBlockRareData::m_percentHeightDescendants contains this LayoutBox.
+    LayoutBlock* m_percentHeightContainer;
 };
 
 // LayoutBox implements the full CSS box model.
@@ -849,6 +857,15 @@ public:
 
     void clearPreviousPaintInvalidationRects() override;
 
+    LayoutBlock* positionedContainer() const { return m_rareData ? m_rareData->m_positionedContainer : nullptr; }
+    void setPositionedContainer(LayoutBlock*);
+    void removeFromPositionedContainer();
+
+    LayoutBlock* percentHeightContainer() const { return m_rareData ? m_rareData->m_percentHeightContainer : nullptr; }
+    void setPercentHeightContainer(LayoutBlock*);
+    void removeFromPercentHeightContainer();
+    void clearPercentHeightDescendants();
+
 protected:
     void willBeDestroyed() override;
 
@@ -887,6 +904,15 @@ protected:
     bool hasNonCompositedScrollbars() const final;
     void excludeScrollbars(LayoutRect&, OverlayScrollbarSizeRelevancy = IgnoreOverlayScrollbarSize) const;
 
+    LayoutBoxRareData* rareData() const { return m_rareData.get(); }
+    LayoutBoxRareData& ensureRareData()
+    {
+        if (!m_rareData)
+            m_rareData = adoptPtr(createRareData());

[esprehn, 2016/01/06 19:37:25]

adoptPtr should be at the creation site, not around a virtual call.

[Xianzhu, 2016/01/06 20:49:07]

Done.

+        return *m_rareData.get();
+    }
+    virtual LayoutBoxRareData* createRareData() { return new LayoutBoxRareData; }

[esprehn, 2016/01/06 19:37:25]

PassOwnPtr, you should never leak like this.

[Xianzhu, 2016/01/06 20:49:07]

Done.

+
 private:
     bool mustInvalidateBackgroundOrBorderPaintOnHeightChange() const;
     bool mustInvalidateBackgroundOrBorderPaintOnWidthChange() const;
@@ -937,13 +963,6 @@ private:
     // details about those widths.
     virtual void computePreferredLogicalWidths() { clearPreferredLogicalWidthsDirty(); }
 
-    LayoutBoxRareData& ensureRareData()
-    {
-        if (!m_rareData)
-            m_rareData = adoptPtr(new LayoutBoxRareData());
-        return *m_rareData.get();
-    }
-
     bool needToSavePreviousBoxSizes();
     void savePreviousBoxSizesIfNeeded();
     LayoutSize computePreviousBorderBoxSize(const LayoutSize& previousBoundsSize) const;