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

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 4056 matching lines @@
 }
 
 void RenderBox::addLayoutOverflow(const LayoutRect& rect)
 {
     LayoutRect clientBox = noOverflowRect();
     if (clientBox.contains(rect) || rect.isEmpty())
         return;
 
     // 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()));
 
     m_overflow->addLayoutOverflow(overflowRect);
 }
 
 void RenderBox::addVisualOverflow(const LayoutRect& rect)
 {
     LayoutRect borderBox = borderBoxRect();
@@ skipping 406 matching lines @@
     computedValues.m_margins.m_end = marginEnd();
 
     setLogicalTop(oldLogicalTop);
     setLogicalWidth(oldLogicalWidth);
     setLogicalLeft(oldLogicalLeft);
     setMarginLeft(oldMarginLeft);
     setMarginRight(oldMarginRight);
 }
 
 } // namespace blink