Don't clamp scroll positions until the end of all layouts

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. 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
  * License as published by the Free Software Foundation; either
@@ skipping 841 matching lines @@
 void LayoutBlock::startDelayUpdateScrollInfo()
 {
     if (gDelayUpdateScrollInfo == 0) {
         ASSERT(!gDelayedUpdateScrollInfoSet);
         gDelayedUpdateScrollInfoSet = new DelayedUpdateScrollInfoSet;
     }
     ASSERT(gDelayedUpdateScrollInfoSet);
     ++gDelayUpdateScrollInfo;
 }
 
-bool LayoutBlock::finishDelayUpdateScrollInfo(SubtreeLayoutScope* layoutScope)
+bool LayoutBlock::finishDelayUpdateScrollInfo(SubtreeLayoutScope* layoutScope, ScrollPositionMap* scrollMap)
 {
     bool childrenMarkedForRelayout = false;
 
     --gDelayUpdateScrollInfo;
     ASSERT(gDelayUpdateScrollInfo >= 0);
     if (gDelayUpdateScrollInfo == 0) {
         ASSERT(gDelayedUpdateScrollInfoSet);
 
         OwnPtr<DelayedUpdateScrollInfoSet> infoSet(adoptPtr(gDelayedUpdateScrollInfoSet));
         gDelayedUpdateScrollInfoSet = nullptr;
 
         for (auto* block : *infoSet) {
             if (block->hasOverflowClip()) {
-                childrenMarkedForRelayout |= block->layer()->getScrollableArea()->updateAfterLayout(layoutScope);
+                PaintLayerScrollableArea* scrollableArea = block->layer()->getScrollableArea();
+                if (scrollMap)
+                    scrollMap->add(scrollableArea, scrollableArea->scrollPositionDouble());
+                childrenMarkedForRelayout |= scrollableArea->updateAfterLayout(layoutScope);
             }
         }
     }
     return childrenMarkedForRelayout;
 }
 
 void LayoutBlock::updateScrollInfoAfterLayout()
 {
     if (hasOverflowClip()) {
         if (style()->isFlippedBlocksWritingMode()) {
@@ skipping 1979 matching lines @@
 void LayoutBlock::showLineTreeAndMark(const InlineBox* markedBox1, const char* markedLabel1, const InlineBox* markedBox2, const char* markedLabel2, const LayoutObject* obj) const
 {
     showLayoutObject();
     for (const RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox())
         root->showLineTreeAndMark(markedBox1, markedLabel1, markedBox2, markedLabel2, obj, 1);
 }
 
 #endif
 
 } // namespace blink