Improve positioned/percentHeight descendant/container tracking

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

Index: third_party/WebKit/Source/core/layout/LayoutBlock.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutBlock.h b/third_party/WebKit/Source/core/layout/LayoutBlock.h
index dbfe957fab3dc189f4fca56c4b4cd51438ab5f18..f40b4db8a2696bcb1fd2f6f4102c37dc5388879f 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBlock.h
+++ b/third_party/WebKit/Source/core/layout/LayoutBlock.h
@@ -44,7 +44,7 @@ class WordMeasurement;
 
 typedef WTF::ListHashSet<LayoutBox*, 16> TrackedLayoutBoxListHashSet;
 typedef WTF::HashMap<const LayoutBlock*, OwnPtr<TrackedLayoutBoxListHashSet>> TrackedDescendantsMap;
-typedef WTF::HashMap<const LayoutBox*, OwnPtr<HashSet<LayoutBlock*>>> TrackedContainerMap;
+typedef WTF::HashMap<const LayoutBox*, LayoutBlock*> TrackedContainerMap;
 typedef Vector<WordMeasurement, 64> WordMeasurements;
 
 enum ContainingBlockState { NewContainingBlock, SameContainingBlock };
@@ -159,25 +159,22 @@ public:
     static void removePositionedObject(LayoutBox*);
     void removePositionedObjects(LayoutBlock*, ContainingBlockState = SameContainingBlock);
 
-    TrackedLayoutBoxListHashSet* positionedObjects() const;
+    TrackedLayoutBoxListHashSet* positionedObjects() const { return hasPositionedObjects() ? positionedObjectsInternal() : nullptr; }
     bool hasPositionedObjects() const
     {
-        TrackedLayoutBoxListHashSet* objects = positionedObjects();
-        return objects && !objects->isEmpty();
+        ASSERT(static_cast<bool>(m_hasPositionedObjects) == (positionedObjectsInternal() && !positionedObjectsInternal()->isEmpty()));
+        return m_hasPositionedObjects;
     }
 
     void addPercentHeightDescendant(LayoutBox*);
-    static void removePercentHeightDescendant(LayoutBox*);
-    static bool hasPercentHeightContainerMap();
-    static bool hasPercentHeightDescendant(LayoutBox*);
-    static void clearPercentHeightDescendantsFrom(LayoutBox*);
-    static void removePercentHeightDescendantIfNeeded(LayoutBox*);
+    void removePercentHeightDescendant(LayoutBox*);
+    bool hasPercentHeightDescendant(LayoutBox* o) const { return hasPercentHeightDescendants() && percentHeightDescendants()->contains(o); }

[esprehn, 2016/01/20 00:01:49]

this checks the bit twice, you want to call the Internal() one here.

[Xianzhu, 2016/01/20 02:33:26]

Done.

 
-    TrackedLayoutBoxListHashSet* percentHeightDescendants() const;
+    TrackedLayoutBoxListHashSet* percentHeightDescendants() const { return hasPercentHeightDescendants() ? percentHeightDescendantsInternal() : nullptr; }
     bool hasPercentHeightDescendants() const
     {
-        TrackedLayoutBoxListHashSet* descendants = percentHeightDescendants();
-        return descendants && !descendants->isEmpty();
+        ASSERT(static_cast<bool>(m_hasPercentHeightDescendants) == (percentHeightDescendantsInternal() && !percentHeightDescendantsInternal()->isEmpty()));

[esprehn, 2016/01/20 00:01:48]

I would do this as:

(!m_hasPercentHeightDescendants || (percentHeightDescendantsInternal() &&
percentHeightDescendantsInternal()->isEmpty()))

[Xianzhu, 2016/01/20 02:33:26]

This will miss check of another side: when m_hasPercentHeightDescendants is true
then percentHeightDescendantsInternal() should be null.

Changed to
ASSERT(m_hasPercentHeightDescendants ? percentHeightDescendantsInternal() &&
!percentHeightDescendantsInternal()->isEmpty() :
!percentHeightDescendantsInternal());

+        return m_hasPercentHeightDescendants;
     }
 
     void notifyScrollbarThicknessChanged() { m_widthAvailableToChildrenChanged = true; }
@@ -399,8 +396,9 @@ private:
 
     bool isSelfCollapsingBlock() const override;
 
-    void insertIntoTrackedLayoutBoxMaps(LayoutBox* descendant, TrackedDescendantsMap*&, TrackedContainerMap*&);
-    static void removeFromTrackedLayoutBoxMaps(LayoutBox* descendant, TrackedDescendantsMap*&, TrackedContainerMap*&);
+    void insertIntoTrackedDescendantsMap(LayoutBox*, TrackedDescendantsMap*&);
+    TrackedLayoutBoxListHashSet* positionedObjectsInternal() const;
+    TrackedLayoutBoxListHashSet* percentHeightDescendantsInternal() const;
 
     Node* nodeForHitTest() const;
 
@@ -496,6 +494,9 @@ protected:
     mutable unsigned m_descendantsWithFloatsMarkedForLayout : 1;
     mutable unsigned m_needsRecalcLogicalWidthAfterLayoutChildren : 1;
 
+    unsigned m_hasPositionedObjects : 1;
+    unsigned m_hasPercentHeightDescendants : 1;
+
     // LayoutRubyBase objects need to be able to split and merge, moving their children around
     // (calling moveChildTo, moveAllChildrenTo, and makeChildrenNonInline).
     friend class LayoutRubyBase;