Fix incorrect percentage top for positioned elements.

Source/core/layout/LayoutBox.h

Index: Source/core/layout/LayoutBox.h
diff --git a/Source/core/layout/LayoutBox.h b/Source/core/layout/LayoutBox.h
index 0310e4415eaf635a9e75dbe0101ecdaac40ebace..99a3260891a8034a3b4691ce40135e0791c6fbb8 100644
--- a/Source/core/layout/LayoutBox.h
+++ b/Source/core/layout/LayoutBox.h
@@ -476,6 +476,8 @@ public:
     virtual void mapRectToPaintInvalidationBacking(const LayoutBoxModelObject* paintInvalidationContainer, LayoutRect&, const PaintInvalidationState*) const override;
     virtual void invalidatePaintForOverhangingFloats(bool paintAllDescendants);
 
+    LayoutUnit containingBlockLogicalHeight() const;

[mstensho (USE GERRIT), 2015/03/26 12:53:37]

Need a more descriptive name, so that nobody gets tempted to use it during
layout.

containingBlockLogicalHeightForComputedStyleResolution(), or something less ugly
if you can think of something.

[changseok, 2015/03/30 07:17:57]

I'm not good at naming anything too. :p How about just
containingBlockLogicalheightForComputedStyle()?

[mstensho (USE GERRIT), 2015/04/13 21:40:04]

Sounds good.

[Timothy Loh, 2015/04/14 09:57:48]

This name is misleading. Maybe [...]ForGetComputedStyle? The ComputedStyle
object stores computed values, while getComputedStyle returns what are now
called resolved values. This is equal to the computed value for most properties,
but in a select few cases (e.g. top) returns something else.

http://dev.w3.org/csswg/cssom/#resolved-values

+
     virtual LayoutUnit containingBlockLogicalWidthForContent() const override;
     LayoutUnit containingBlockLogicalHeightForContent(AvailableLogicalHeightType) const;