[css-grid] mimax(auto, <flex>) should be serialized as <flex>

third_party/WebKit/Source/core/css/ComputedStyleCSSValueMapping.cpp

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc.
  * All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2011 Sencha, Inc. All rights reserved.
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 847 matching lines @@
   return zoomAdjustedPixelValueForLength(trackBreadthLength, style);
 }
 
 static CSSValue* specifiedValueForGridTrackSize(const GridTrackSize& trackSize,
                                                 const ComputedStyle& style) {
   switch (trackSize.type()) {
     case LengthTrackSizing:
       return specifiedValueForGridTrackBreadth(trackSize.minTrackBreadth(),
                                                style);
     case MinMaxTrackSizing: {
+      if (trackSize.minTrackBreadth().isAuto() &&
+          trackSize.maxTrackBreadth().isFlex()) {
+        return CSSPrimitiveValue::create(trackSize.maxTrackBreadth().flex(),
+                                         CSSPrimitiveValue::UnitType::Fraction);
+      }
+
       auto* minMaxTrackBreadths = CSSFunctionValue::create(CSSValueMinmax);
       minMaxTrackBreadths->append(*specifiedValueForGridTrackBreadth(
           trackSize.minTrackBreadth(), style));
       minMaxTrackBreadths->append(*specifiedValueForGridTrackBreadth(
           trackSize.maxTrackBreadth(), style));
       return minMaxTrackBreadths;
     }
     case FitContentTrackSizing: {
       auto* fitContentTrackBreadth =
           CSSFunctionValue::create(CSSValueFitContent);
@@ skipping 2735 matching lines @@
     case CSSPropertyAll:
       return nullptr;
     default:
       break;
   }
   ASSERT_NOT_REACHED();
   return nullptr;
 }
 
 }  // namespace blink