Refactor scroll updates during flexbox layout.

third_party/WebKit/Source/core/layout/LayoutDeprecatedFlexibleBox.cpp

 /*
  * This file is part of the layout object implementation for KHTML.
  *
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 405 matching lines @@
 
     LayoutUnit remainingSpace;
 
 
     FlexBoxIterator iterator(this);
     unsigned highestFlexGroup = 0;
     unsigned lowestFlexGroup = 0;
     bool haveFlex = false, flexingChildren = false;
     gatherFlexChildrenInfo(iterator, relayoutChildren, highestFlexGroup, lowestFlexGroup, haveFlex);
 
-    LayoutBlock::startDelayUpdateScrollInfo();
+    PaintLayerScrollableArea::DelayScrollPositionClampScope delayClampScope;
 
     // We do 2 passes.  The first pass is simply to lay everyone out at
     // their preferred widths.  The second pass handles flexing the children.
     do {
         // Reset our height.
         setHeight(yPos);
 
         xPos = borderLeft() + paddingLeft();
 
         // Our first pass is done without flexing.  We simply lay the children
@@ skipping 202 matching lines @@
                     }
                 } while (absoluteValue(groupRemainingSpace) >= 1);
             }
 
             // We didn't find any children that could grow.
             if (haveFlex && !flexingChildren)
                 haveFlex = false;
         }
     } while (haveFlex);
 
-    LayoutBlock::finishDelayUpdateScrollInfo(nullptr, nullptr);
-
     if (remainingSpace > 0 && ((style()->isLeftToRightDirection() && style()->boxPack() != BoxPackStart)
         || (!style()->isLeftToRightDirection() && style()->boxPack() != BoxPackEnd))) {
         // Children must be repositioned.
         LayoutUnit offset;
         if (style()->boxPack() == BoxPackJustify) {
             // Determine the total number of children.
             int totalChildren = 0;
             for (LayoutBox* child = iterator.first(); child; child = iterator.next()) {
                 if (childDoesNotAffectWidthOrFlexing(child))
                     continue;
@@ skipping 55 matching lines @@
     unsigned lowestFlexGroup = 0;
     bool haveFlex = false, flexingChildren = false;
     gatherFlexChildrenInfo(iterator, relayoutChildren, highestFlexGroup, lowestFlexGroup, haveFlex);
 
     // We confine the line clamp ugliness to vertical flexible boxes (thus keeping it out of
     // mainstream block layout); this is not really part of the XUL box model.
     bool haveLineClamp = !style()->lineClamp().isNone();
     if (haveLineClamp)
         applyLineClamp(iterator, relayoutChildren);
 
-    LayoutBlock::startDelayUpdateScrollInfo();
+    PaintLayerScrollableArea::DelayScrollPositionClampScope delayClampScope;
 
     // We do 2 passes.  The first pass is simply to lay everyone out at
     // their preferred widths.  The second pass handles flexing the children.
     // Our first pass is done without flexing.  We simply lay the children
     // out within the box.
     do {
         setHeight(borderTop() + paddingTop());
         LayoutUnit minHeight = size().height() + toAdd;
 
         for (LayoutBox* child = iterator.first(); child; child = iterator.next()) {
@@ skipping 153 matching lines @@
                     }
                 } while (absoluteValue(groupRemainingSpace) >= 1);
             }
 
             // We didn't find any children that could grow.
             if (haveFlex && !flexingChildren)
                 haveFlex = false;
         }
     } while (haveFlex);
 
-    LayoutBlock::finishDelayUpdateScrollInfo(nullptr, nullptr);
-
     if (style()->boxPack() != BoxPackStart && remainingSpace > 0) {
         // Children must be repositioned.
         LayoutUnit offset;
         if (style()->boxPack() == BoxPackJustify) {
             // Determine the total number of children.
             int totalChildren = 0;
             for (LayoutBox* child = iterator.first(); child; child = iterator.next()) {
                 if (childDoesNotAffectWidthOrFlexing(child))
                     continue;
 
@@ skipping 200 matching lines @@
     if (minHeight.isFixed() || minHeight.isAuto()) {
         LayoutUnit minHeight(child->style()->minHeight().value());
         LayoutUnit height = contentHeightForChild(child);
         LayoutUnit allowedShrinkage = (minHeight - height).clampPositiveToZero();
         return allowedShrinkage;
     }
     return LayoutUnit();
 }
 
 } // namespace blink