Percentage heights can be resolved against any parent if writing mode is orthogonal.

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 2341 matching lines @@
     }
     if (height.isFixed())
         return height.value();
     if (height.isPercent())
         return computePercentageLogicalHeight(height);
     return -1;
 }
 
 bool RenderBox::skipContainingBlockForPercentHeightCalculation(const RenderBox* containingBlock) const
 {
+    // If the writing mode of the containing block is orthogonal to ours, it means that we shouldn't
+    // skip anything, since we're going to resolve the percentage height against a containing block *width*.
+    if (isHorizontalWritingMode() != containingBlock->isHorizontalWritingMode())
+        return false;
+
     // Flow threads for multicol or paged overflow should be skipped. They are invisible to the DOM,
     // and percent heights of children should be resolved against the multicol or paged container.
     if (containingBlock->isRenderFlowThread())
         return true;
 
     // For quirks mode and anonymous blocks, we skip auto-height containingBlocks when computing percentages.
     // For standards mode, we treat the percentage as auto if it has an auto-height containing block.
     if (!document().inQuirksMode() && !containingBlock->isAnonymousBlock())
         return false;
-    return !containingBlock->isTableCell() && !containingBlock->isOutOfFlowPositioned() && containingBlock->style()->logicalHeight().isAuto() && isHorizontalWritingMode() == containingBlock->isHorizontalWritingMode();
+
+    return !containingBlock->isTableCell() && !containingBlock->isOutOfFlowPositioned() && containingBlock->style()->logicalHeight().isAuto();
 }
 
 LayoutUnit RenderBox::computePercentageLogicalHeight(const Length& height) const
 {
     LayoutUnit availableHeight = -1;
 
     bool skippedAutoHeightContainingBlock = false;
     RenderBlock* cb = containingBlock();
     const RenderBox* containingBlockChild = this;
     LayoutUnit rootMarginBorderPaddingHeight = 0;
@@ skipping 2139 matching lines @@
     computedValues.m_margins.m_end = marginEnd();
 
     setLogicalTop(oldLogicalTop);
     setLogicalWidth(oldLogicalWidth);
     setLogicalLeft(oldLogicalLeft);
     setMarginLeft(oldMarginLeft);
     setMarginRight(oldMarginRight);
 }
 
 } // namespace blink