Don't let current width affect preferred width on shrink-to-fit containers

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 2706 matching lines @@
   LayoutUnit logicalWidthResult =
       fillAvailableMeasure(availableLogicalWidth, marginStart, marginEnd);
 
   if (shrinkToAvoidFloats() && cb->isLayoutBlockFlow() &&
       toLayoutBlockFlow(cb)->containsFloats())
     logicalWidthResult = std::min(
         logicalWidthResult, shrinkLogicalWidthToAvoidFloats(
                                 marginStart, marginEnd, toLayoutBlockFlow(cb)));
 
   if (widthType == MainOrPreferredSize &&
-      sizesLogicalWidthToFitContent(logicalWidth))
+      sizesLogicalWidthToFitContent(logicalWidth)) {
+    // Reset width so that any percent margins on inline children do not
+    // use it when calculating min/max preferred width.

[eae, 2017/04/10 05:17:57]

Would you mind filing a bug about this const_cast and adding a FIXME here?
Thanks!

+    const_cast<LayoutBox*>(this)->setLogicalWidth(LayoutUnit());
     return std::max(minPreferredLogicalWidth(),
                     std::min(maxPreferredLogicalWidth(), logicalWidthResult));
+  }
   return logicalWidthResult;
 }
 
 bool LayoutBox::columnFlexItemHasStretchAlignment() const {
   // auto margins mean we don't stretch. Note that this function will only be
   // used for widths, so we don't have to check marginBefore/marginAfter.
   const auto& parentStyle = parent()->styleRef();
   DCHECK(parentStyle.isColumnFlexDirection());
   if (styleRef().marginStart().isAuto() || styleRef().marginEnd().isAuto())
     return false;
@@ skipping 3016 matching lines @@
 
 void LayoutBox::MutableForPainting::
     savePreviousContentBoxSizeAndLayoutOverflowRect() {
   auto& rareData = layoutBox().ensureRareData();
   rareData.m_hasPreviousContentBoxSizeAndLayoutOverflowRect = true;
   rareData.m_previousContentBoxSize = layoutBox().contentBoxRect().size();
   rareData.m_previousLayoutOverflowRect = layoutBox().layoutOverflowRect();
 }
 
 }  // namespace blink