[WIP] Identifies the part of the code that makes left/top overflow invisible.

Source/core/rendering/RenderBox.cpp

Index: Source/core/rendering/RenderBox.cpp
diff --git a/Source/core/rendering/RenderBox.cpp b/Source/core/rendering/RenderBox.cpp
index b4c3939d511b886855b77a039883d27d13d96512..45e6500c651942972bf95c8353d75b63751ab04c 100644
--- a/Source/core/rendering/RenderBox.cpp
+++ b/Source/core/rendering/RenderBox.cpp
@@ -4074,34 +4074,6 @@ void RenderBox::addLayoutOverflow(const LayoutRect& rect)
 
     // For overflow clip objects, we don't want to propagate overflow into unreachable areas.
     LayoutRect overflowRect(rect);
-    if (hasOverflowClip() || isRenderView()) {
-        // Overflow is in the block's coordinate space and thus is flipped for horizontal-bt and vertical-rl
-        // writing modes.  At this stage that is actually a simplification, since we can treat horizontal-tb/bt as the same
-        // and vertical-lr/rl as the same.
-        bool hasTopOverflow = !style()->isLeftToRightDirection() && !isHorizontalWritingMode();
-        bool hasLeftOverflow = !style()->isLeftToRightDirection() && isHorizontalWritingMode();
-        if (isFlexibleBox() && style()->isReverseFlexDirection()) {
-            RenderFlexibleBox* flexibleBox = toRenderFlexibleBox(this);
-            if (flexibleBox->isHorizontalFlow())
-                hasLeftOverflow = true;
-            else
-                hasTopOverflow = true;
-        }
-
-        if (!hasTopOverflow)
-            overflowRect.shiftYEdgeTo(std::max(overflowRect.y(), clientBox.y()));
-        else
-            overflowRect.shiftMaxYEdgeTo(std::min(overflowRect.maxY(), clientBox.maxY()));
-        if (!hasLeftOverflow)
-            overflowRect.shiftXEdgeTo(std::max(overflowRect.x(), clientBox.x()));
-        else
-            overflowRect.shiftMaxXEdgeTo(std::min(overflowRect.maxX(), clientBox.maxX()));
-
-        // Now re-test with the adjusted rectangle and see if it has become unreachable or fully
-        // contained.
-        if (clientBox.contains(overflowRect) || overflowRect.isEmpty())
-            return;
-    }
 
     if (!m_overflow)
         m_overflow = adoptPtr(new RenderOverflow(clientBox, borderBoxRect()));