[CSS Grid Layout] Do not stretch always grid items with auto width

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
  * modify it under the terms of the GNU Library General Public
@@ skipping 1903 matching lines @@
 
     if (isOutOfFlowPositioned()) {
         computePositionedLogicalWidth(computedValues);
         return;
     }
 
     // The parent box is flexing us, so it has increased or decreased our
     // width.  Use the width from the style context.
     // FIXME: Account for writing-mode in flexible boxes.
     // https://bugs.webkit.org/show_bug.cgi?id=46418
-    if (hasOverrideLogicalContentWidth() && parent()->isFlexibleBoxIncludingDeprecated()) {
+    if (hasOverrideLogicalContentWidth() && (parent()->isFlexibleBoxIncludingDeprecated() || parent()->isLayoutGrid())) {

[Manuel Rego, 2015/07/13 12:40:07]

This if here worries me as the code to manage "min-width: auto"; is a few lines
below.

Actually I've been checking a few cases that are breaking "min-width: auto;"
behavior:
* http://jsbin.com/rowabah/1/edit?html,css,output
* http://jsbin.com/mawovey/1/edit?html,css,output 

         computedValues.m_extent = overrideLogicalContentWidth() + borderAndPaddingLogicalWidth();
         return;
     }
 
     // FIXME: Account for writing-mode in flexible boxes.
     // https://bugs.webkit.org/show_bug.cgi?id=46418
     bool inVerticalBox = parent()->isDeprecatedFlexibleBox() && (parent()->style()->boxOrient() == VERTICAL);
     bool stretching = (parent()->style()->boxAlign() == BSTRETCH);
     bool treatAsReplaced = shouldComputeSizeAsReplaced() && (!inVerticalBox || !stretching);
 
@@ skipping 2834 matching lines @@
 bool LayoutBox::canRenderBorderImage() const
 {
     if (!style()->hasBorderDecoration())
         return false;
 
     StyleImage* borderImage = style()->borderImage().image();
     return borderImage && borderImage->canRender(*this, style()->effectiveZoom()) && borderImage->isLoaded();
 }
 
 } // namespace blink