Don't update height in LayoutBlock::markFixedPositionObjectForLayoutIfNeeded.

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
@@ skipping 672 matching lines @@
   bool hasStaticBlockPosition =
       child->style()->hasStaticBlockPosition(isHorizontalWritingMode());
   bool hasStaticInlinePosition =
       child->style()->hasStaticInlinePosition(isHorizontalWritingMode());
   if (!hasStaticBlockPosition && !hasStaticInlinePosition)
     return;
 
   LayoutObject* o = child->parent();
   while (o && !o->isLayoutView() && o->style()->position() != AbsolutePosition)
     o = o->parent();
-  if (o->style()->position() != AbsolutePosition)
+  // The LayoutView is absolute-positioned, but does not move.
+  if (o->isLayoutView())
     return;
 
+  // We must compute child's width and height, but not update them now.
+  // The child will update its width and height when it gets laid out, and needs
+  // to see them change there.
   LayoutBox* box = toLayoutBox(child);
   if (hasStaticInlinePosition) {
     LogicalExtentComputedValues computedValues;
     box->computeLogicalWidth(computedValues);
     LayoutUnit newLeft = computedValues.m_position;
     if (newLeft != box->logicalLeft())
       layoutScope.setChildNeedsLayout(child);
   } else if (hasStaticBlockPosition) {
-    LayoutUnit oldTop = box->logicalTop();
-    box->updateLogicalHeight();
-    if (box->logicalTop() != oldTop)
+    LogicalExtentComputedValues computedValues;
+    box->computeLogicalHeight(computedValues);
+    LayoutUnit newTop = computedValues.m_position;
+    if (newTop != box->logicalTop())
       layoutScope.setChildNeedsLayout(child);
   }
 }
 
 LayoutUnit LayoutBlock::marginIntrinsicLogicalWidthForChild(
     const LayoutBox& child) const {
   // A margin has three types: fixed, percentage, and auto (variable).
   // Auto and percentage margins become 0 when computing min/max width.
   // Fixed margins can be added in as is.
   Length marginLeft = child.style()->marginStartUsing(style());
@@ skipping 38 matching lines @@
   TrackedLayoutBoxListHashSet* positionedDescendants = positionedObjects();
   if (!positionedDescendants)
     return;
 
   bool isPaginated = view()->layoutState()->isPaginated();
 
   for (auto* positionedObject : *positionedDescendants) {
     positionedObject->setMayNeedPaintInvalidation();
 
     SubtreeLayoutScope layoutScope(*positionedObject);
-    // A fixed position element with an absolute positioned ancestor has no way
-    // of knowing if the latter has changed position. So if this is a fixed
-    // position element, mark it for layout if it has an abspos ancestor and
-    // needs to move with that ancestor, i.e. it has static position.
+    // If positionedObject is fixed-position and moves with an absolute-

[mstensho (USE GERRIT), 2016/10/19 18:24:30]

"fixed-positioned"

[skobes, 2016/10/19 21:48:40]

Done.

+    // positioned ancestor (other than the LayoutView, which cannot move),
+    // mark it for layout now.
     markFixedPositionObjectForLayoutIfNeeded(positionedObject, layoutScope);
     if (info == LayoutOnlyFixedPositionedObjects) {
       positionedObject->layoutIfNeeded();
       continue;
     }
 
     if (!positionedObject->normalChildNeedsLayout() &&
         (relayoutChildren || m_heightAvailableToChildrenChanged ||
          needsLayoutDueToStaticPosition(positionedObject)))
       layoutScope.setChildNeedsLayout(positionedObject);
@@ skipping 1429 matching lines @@
   }
 
   return availableHeight;
 }
 
 bool LayoutBlock::hasDefiniteLogicalHeight() const {
   return availableLogicalHeightForPercentageComputation() != LayoutUnit(-1);
 }
 
 }  // namespace blink