Reduce invalidation on children-needs-layout containers

Source/core/rendering/RenderObject.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 389 matching lines @@
     void setHasColumns(bool b = true) { m_bitfields.setHasColumns(b); }
 
     bool ancestorLineBoxDirty() const { return m_bitfields.ancestorLineBoxDirty(); }
     void setAncestorLineBoxDirty(bool value = true)
     {
         m_bitfields.setAncestorLineBoxDirty(value);
         if (value)
             setNeedsLayout();
     }
 
+    bool hasNothingToPaint() const { return m_bitfields.hasNothingToPaint(); }
+    void setHasNothingToPaint(bool b) { return m_bitfields.setHasNothingToPaint(b); }
+
     enum FlowThreadState {
         NotInsideFlowThread = 0,
         InsideOutOfFlowThread = 1,
         InsideInFlowThread = 2,
     };
 
     void setFlowThreadStateIncludingDescendants(FlowThreadState);
 
     FlowThreadState flowThreadState() const { return m_bitfields.flowThreadState(); }
     void setFlowThreadState(FlowThreadState state) { m_bitfields.setFlowThreadState(state); }
@@ skipping 98 matching lines @@
         HasBoxDecorationsAndBackgroundIsKnownToBeObscured,
         HasBoxDecorationsAndBackgroundMayBeVisible,
     };
     bool hasBoxDecorations() const { return m_bitfields.boxDecorationState() != NoBoxDecorations; }
     bool backgroundIsKnownToBeObscured();
     bool borderImageIsLoadedAndCanBeRendered() const;
     bool mustRepaintBackgroundOrBorder() const;
     bool hasBackground() const { return style()->hasBackground(); }
     bool hasEntirelyFixedBackground() const;
 
+    bool needsLayoutBecauseOfChildren() const { return needsLayout() && !selfNeedsLayout() && !needsPositionedMovementLayout() && !needsSimplifiedNormalFlowLayout(); }
+
     bool needsLayout() const
     {
         return m_bitfields.selfNeedsLayout() || m_bitfields.normalChildNeedsLayout() || m_bitfields.posChildNeedsLayout()
             || m_bitfields.needsSimplifiedNormalFlowLayout() || m_bitfields.needsPositionedMovementLayout();
     }
 
     bool selfNeedsLayout() const { return m_bitfields.selfNeedsLayout(); }
     bool needsPositionedMovementLayout() const { return m_bitfields.needsPositionedMovementLayout(); }
     bool needsPositionedMovementLayoutOnly() const
     {
@@ skipping 579 matching lines @@
             , m_isReplaced(false)
             , m_horizontalWritingMode(true)
             , m_isDragging(false)
             , m_hasLayer(false)
             , m_hasOverflowClip(false)
             , m_hasTransform(false)
             , m_hasReflection(false)
             , m_hasCounterNodeMap(false)
             , m_everHadLayout(false)
             , m_ancestorLineBoxDirty(false)
+            , m_hasNothingToPaint(false)
             , m_childrenInline(false)
             , m_hasColumns(false)
             , m_layoutDidGetCalled(false)
             , m_positionedState(IsStaticallyPositioned)
             , m_selectionState(SelectionNone)
             , m_flowThreadState(NotInsideFlowThread)
             , m_boxDecorationState(NoBoxDecorations)
             , m_hasPendingResourceUpdate(false)
         {
         }
@@ skipping 19 matching lines @@
 
         ADD_BOOLEAN_BITFIELD(hasLayer, HasLayer);
         ADD_BOOLEAN_BITFIELD(hasOverflowClip, HasOverflowClip); // Set in the case of overflow:auto/scroll/hidden
         ADD_BOOLEAN_BITFIELD(hasTransform, HasTransform);
         ADD_BOOLEAN_BITFIELD(hasReflection, HasReflection);
 
         ADD_BOOLEAN_BITFIELD(hasCounterNodeMap, HasCounterNodeMap);
         ADD_BOOLEAN_BITFIELD(everHadLayout, EverHadLayout);
         ADD_BOOLEAN_BITFIELD(ancestorLineBoxDirty, AncestorLineBoxDirty);
 
+        ADD_BOOLEAN_BITFIELD(hasNothingToPaint, HasNothingToPaint);
+
         // from RenderBlock
         ADD_BOOLEAN_BITFIELD(childrenInline, ChildrenInline);
         ADD_BOOLEAN_BITFIELD(hasColumns, HasColumns);
 
         ADD_BOOLEAN_BITFIELD(layoutDidGetCalled, LayoutDidGetCalled);
 
     private:
         unsigned m_positionedState : 2; // PositionedState
         unsigned m_selectionState : 3; // SelectionState
         unsigned m_flowThreadState : 2; // FlowThreadState
@@ skipping 241 matching lines @@
 void showTree(const WebCore::RenderObject*);
 void showLineTree(const WebCore::RenderObject*);
 void showRenderTree(const WebCore::RenderObject* object1);
 // We don't make object2 an optional parameter so that showRenderTree
 // can be called from gdb easily.
 void showRenderTree(const WebCore::RenderObject* object1, const WebCore::RenderObject* object2);
 
 #endif
 
 #endif // RenderObject_h