Merge 120859 - REGRESSION(r113885): Margin not properly applied to elements with align=center

Source/WebCore/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.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 1887 matching lines @@
     if (isFloating() || isInline()) {
         // Inline blocks/tables and floats don't have their margins increased.
         containingBlock->setMarginStartForChild(this, minimumValueForLength(marginStartLength, containerWidth, renderView));
         containingBlock->setMarginEndForChild(this, minimumValueForLength(marginEndLength, containerWidth, renderView));
         return;
     }
 
     // Case One: The object is being centered in the containing block's available logical width.
     if ((marginStartLength.isAuto() && marginEndLength.isAuto() && childWidth < containerWidth)
         || (!marginStartLength.isAuto() && !marginEndLength.isAuto() && containingBlock->style()->textAlign() == WEBKIT_CENTER)) {
-        containingBlock->setMarginStartForChild(this, max<LayoutUnit>(0, (containerWidth - childWidth) / 2));
-        containingBlock->setMarginEndForChild(this, containerWidth - childWidth - containingBlock->marginStartForChild(this));
+        // Other browsers center the margin box for align=center elements so we match them here.
+        LayoutUnit marginStartWidth = marginStartLength.value();
+        LayoutUnit marginEndWidth = marginEndLength.value();
+        LayoutUnit centeredMarginBoxStart = max<LayoutUnit>(0, (containerWidth - childWidth - marginStartWidth - marginEndWidth) / 2);
+        containingBlock->setMarginStartForChild(this, centeredMarginBoxStart + marginStartWidth);
+        containingBlock->setMarginEndForChild(this, containerWidth - childWidth - containingBlock->marginStartForChild(this) + marginEndWidth);
         return;
     } 
     
     // Case Two: The object is being pushed to the start of the containing block's available logical width.
     if (marginEndLength.isAuto() && childWidth < containerWidth) {
         containingBlock->setMarginStartForChild(this, valueForLength(marginStartLength, containerWidth, renderView));
         containingBlock->setMarginEndForChild(this, containerWidth - childWidth - containingBlock->marginStartForChild(this));
         return;
     } 
     
@@ skipping 2127 matching lines @@
     }
 
     if (didSplitParentAnonymousBoxes)
         markBoxForRelayoutAfterSplit(this);
 
     ASSERT(beforeChild->parent() == this);
     return beforeChild;
 }
 
 } // namespace WebCore