Move PreviousBoxGeometries from BoxPaintInvalidator into LayoutBox::m_rareData

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 ca26cdbff78eeb24b3482ae0b87951d8a4fbbdd2..9c15f205fdf61b52cd98de51b70b4ff892d27099 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.h
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.h
@@ -65,6 +65,7 @@ struct LayoutBoxRareData {
         m_overrideLogicalContentHeight(-1),
         m_hasOverrideContainingBlockContentLogicalWidth(false),
         m_hasOverrideContainingBlockContentLogicalHeight(false),
+        m_hasPreviousOtherBoxGeometries(false),
         m_percentHeightContainer(nullptr),
         m_snapContainer(nullptr),
         m_snapAreas(nullptr) {}
@@ -76,8 +77,10 @@ struct LayoutBoxRareData {
   LayoutUnit m_overrideLogicalContentWidth;
   LayoutUnit m_overrideLogicalContentHeight;
 
-  bool m_hasOverrideContainingBlockContentLogicalWidth;
-  bool m_hasOverrideContainingBlockContentLogicalHeight;
+  bool m_hasOverrideContainingBlockContentLogicalWidth : 1;
+  bool m_hasOverrideContainingBlockContentLogicalHeight : 1;
+  bool m_hasPreviousOtherBoxGeometries : 1;

[pdr., 2017/02/22 18:37:54]

I think we have some free bits. WDYT about just splitting this out?
bool m_hasPreviousContentBoxSize : 1
bool m_hasPreviousLayoutOverflowRect : 1

Another alternative would be:
bool m_hasPreviousContentBoxSizeOrLayoutOverflowRect

[Xianzhu, 2017/02/22 18:58:52]

I choose m_hasPreviousContentBoxSizeAndLayoutOverflowRect. When we need to save
either of content box size and layout overflow rect, we can just save both
because we'll definitely allocate m_rareData.

Done.

(We could also save both whenever m_rareData is not null even if no need to
save, but that would make the interface between BoxPaintInvalidator and
LayoutBox complicated, and we must inline the saveXXX function because it would
be hot.)

+
   LayoutUnit m_overrideContainingBlockContentLogicalWidth;
   LayoutUnit m_overrideContainingBlockContentLogicalHeight;
 
@@ -98,6 +101,12 @@ struct LayoutBoxRareData {
 
     return *m_snapAreas;
   }
+
+  // Used by BoxPaintInvalidator. Stores the previous content box size and
+  // layout overflow rect after the last paint invalidation.
+  // These are valid if m_hasPreviousOtherBoxGeometries is true.
+  LayoutSize m_previousContentBoxSize;
+  LayoutRect m_previousLayoutOverflowRect;
 };
 
 // LayoutBox implements the full CSS box model.
@@ -318,7 +327,6 @@ class CORE_EXPORT LayoutBox : public LayoutBoxModelObject {
     return LayoutSize(m_frameRect.x(), m_frameRect.y());
   }
   LayoutSize size() const { return m_frameRect.size(); }
-  LayoutSize previousSize() const { return m_previousSize; }
   IntSize pixelSnappedSize() const { return m_frameRect.pixelSnappedSize(); }
 
   void setLocation(const LayoutPoint& location) {
@@ -1311,19 +1319,36 @@ class CORE_EXPORT LayoutBox : public LayoutBoxModelObject {
 
   class MutableForPainting : public LayoutObject::MutableForPainting {
    public:
-    void setPreviousSize(const LayoutSize& size) {
-      static_cast<LayoutBox&>(m_layoutObject).m_previousSize = size;
+    void savePreviousSize() { layoutBox().m_previousSize = layoutBox().size(); }
+    void savePreviousOtherBoxGeometries();
+    void clearPreviousOtherBoxGeometries() {
+      if (layoutBox().m_rareData)
+        layoutBox().m_rareData->m_hasPreviousOtherBoxGeometries = false;
     }
 
    protected:
     friend class LayoutBox;
     MutableForPainting(const LayoutBox& box)
         : LayoutObject::MutableForPainting(box) {}
+    LayoutBox& layoutBox() { return static_cast<LayoutBox&>(m_layoutObject); }
   };
+
   MutableForPainting getMutableForPainting() const {
     return MutableForPainting(*this);
   }
 
+  LayoutSize previousSize() const { return m_previousSize; }
+  LayoutSize previousContentBoxSize() const {
+    return m_rareData && m_rareData->m_hasPreviousOtherBoxGeometries
+               ? m_rareData->m_previousContentBoxSize
+               : previousSize();
+  }
+  LayoutRect previousLayoutOverflowRect() const {
+    return m_rareData && m_rareData->m_hasPreviousOtherBoxGeometries
+               ? m_rareData->m_previousLayoutOverflowRect
+               : LayoutRect(LayoutPoint(), previousSize());
+  }
+
  protected:
   virtual LayoutRect controlClipRect(const LayoutPoint&) const {
     return LayoutRect();