Fix incorrect percentage top for positioned elements.

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 2699 matching lines @@
     // FIXME: Check logicalTop/logicalBottom here to correctly handle vertical writing-mode.
     // https://bugs.webkit.org/show_bug.cgi?id=46500
     if (isLayoutBlock() && isOutOfFlowPositioned() && style()->height().isAuto() && !(style()->top().isAuto() || style()->bottom().isAuto())) {
         LayoutBlock* block = const_cast<LayoutBlock*>(toLayoutBlock(this));
         LogicalExtentComputedValues computedValues;
         block->computeLogicalHeight(block->logicalHeight(), 0, computedValues);
         LayoutUnit newContentHeight = computedValues.m_extent - block->borderAndPaddingLogicalHeight() - block->scrollbarLogicalHeight();
         return adjustContentBoxLogicalHeightForBoxSizing(newContentHeight);
     }
 
+    if (isLayoutBlock() && isOutOfFlowPositioned() && (heightType == IncludePadding)) {

[rune, 2015/03/13 12:49:13]

What happens if you pass IncludePadding with non-out-of-flow-positioned?

It doesn't look like you handle that at all. Should you just check for
IncludePadding and assert isLayoutBlock() && isOutOfFlowPositioned() instead?

[changseok, 2015/03/16 10:02:25]

IncludePadding is only for position:absolute. so none-out-of-flow-positioned
elements can't have it.
But I think you properly pointed out blinded problems. After rethinking the
lines and testing gecko, I found
this worked weirdly for some cases. Basically below recursive call of
containingBlockLogicalHeightForContent need to be changed with a determinate
method returning logical height. Otherwise viewport height (or page height, i,e
initialContainingBlock in the spec) would be eventually returned for some cases.

+        LayoutUnit availableHeight = containingBlockLogicalHeightForPositioned(this);
+        return adjustContentBoxLogicalHeightForBoxSizing(valueForLength(h, availableHeight));
+    }
+
     // FIXME: This is wrong if the containingBlock has a perpendicular writing mode.
     LayoutUnit availableHeight = containingBlockLogicalHeightForContent(heightType);
     if (heightType == ExcludeMarginBorderPadding) {
         // FIXME: Margin collapsing hasn't happened yet, so this incorrectly removes collapsed margins.
         availableHeight -= marginBefore() + marginAfter() + borderAndPaddingLogicalHeight();
     }
     return availableHeight;
 }
 
 void LayoutBox::computeAndSetBlockDirectionMargins(const LayoutBlock* containingBlock)
@@ skipping 1914 matching lines @@
     computedValues.m_margins.m_end = marginEnd();
 
     setLogicalTop(oldLogicalTop);
     setLogicalWidth(oldLogicalWidth);
     setLogicalLeft(oldLogicalLeft);
     setMarginLeft(oldMarginLeft);
     setMarginRight(oldMarginRight);
 }
 
 } // namespace blink