Don't allow negative width for positioned elements

Source/core/rendering/RenderBox.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 3284 matching lines @@
             if (autoWidthShouldFitContent())
                 shrinkToFitWidth(availableSpace, logicalLeftValue, bordersPlusPadding, computedValues);
             else
                 computedValues.m_extent = availableSpace - (logicalLeftValue + valueForLength(logicalRight, containerLogicalWidth));
         } else if (!logicalLeftIsAuto && !logicalWidthIsAuto && logicalRightIsAuto) {
             // RULE 6: (no need solve for right)
             logicalLeftValue = valueForLength(logicalLeft, containerLogicalWidth);
             computedValues.m_extent = adjustContentBoxLogicalWidthForBoxSizing(valueForLength(logicalWidth, containerLogicalWidth));
         }
     }
+    if (computedValues.m_extent < 0)

[mstensho (USE GERRIT), 2014/09/17 11:48:22]

Might consider moving this to "RULE 5" a few lines further up. Then it will look
more similar to the code in RenderBox::computePositionedLogicalHeightUsing()
(which already has code to avoid negative height).

[Kyungtae Kim, 2014/09/18 12:50:07]

Done.

+        computedValues.m_extent = 0;
 
     // Use computed values to calculate the horizontal position.
 
     // FIXME: This hack is needed to calculate the  logical left position for a 'rtl' relatively
     // positioned, inline because right now, it is using the logical left position
     // of the first line box when really it should use the last line box.  When
     // this is fixed elsewhere, this block should be removed.
     if (containerBlock->isRenderInline() && !containerBlock->style()->isLeftToRightDirection()) {
         const RenderInline* flow = toRenderInline(containerBlock);
         InlineFlowBox* firstLine = flow->firstLineBox();
@@ skipping 1420 matching lines @@
 RenderBox::BoxDecorationData::BoxDecorationData(const RenderStyle& style)
 {
     backgroundColor = style.visitedDependentColor(CSSPropertyBackgroundColor);
     hasBackground = backgroundColor.alpha() || style.hasBackgroundImage();
     ASSERT(hasBackground == style.hasBackground());
     hasBorder = style.hasBorder();
     hasAppearance = style.hasAppearance();
 }
 
 } // namespace blink