SVG does not respect overflow:visible.

Source/core/css/resolver/StyleAdjuster.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 389 matching lines @@
             style->setOverflowX(OVISIBLE);
         if (style->overflowY() != OVISIBLE && style->overflowY() != OHIDDEN)
             style->setOverflowY(OVISIBLE);
     }
 
     // Menulists should have visible overflow
     if (style->appearance() == MenulistPart) {
         style->setOverflowX(OVISIBLE);
         style->setOverflowY(OVISIBLE);
     }
-
-    // Spec: http://www.w3.org/TR/SVG/masking.html#OverflowProperty
-    if (element && element->isSVGElement()) {
-        if (style->overflowY() == OSCROLL)
-            style->setOverflowY(OHIDDEN);
-        else if (style->overflowY() == OAUTO)
-            style->setOverflowY(OVISIBLE);
-
-        if (style->overflowX() == OSCROLL)
-            style->setOverflowX(OHIDDEN);
-        else if (style->overflowX() == OAUTO)
-            style->setOverflowX(OVISIBLE);
-
-        if (style->overflowX() == style->overflowY())
-            return;
-
-        if (style->overflowX() != OVISIBLE)
-            style->setOverflowX(OVISIBLE);
-        else
-            style->setOverflowY(OVISIBLE);
-    }
 }
 
 void StyleAdjuster::adjustStyleForDisplay(RenderStyle* style, RenderStyle* parentStyle)
 {
     if (style->display() == BLOCK && !style->isFloating())
         return;
 
     // FIXME: Don't support this mutation for pseudo styles like first-letter or first-line, since it's not completely
     // clear how that should work.
     if (style->display() == INLINE && style->styleType() == NOPSEUDO && style->writingMode() != parentStyle->writingMode())
@@ skipping 26 matching lines @@
     if (style->writingMode() != TopToBottomWritingMode && (style->display() == BOX || style->display() == INLINE_BOX))
         style->setWritingMode(TopToBottomWritingMode);
 
     if (isDisplayFlexibleBox(parentStyle->display()) || isDisplayGridBox(parentStyle->display())) {
         style->setFloating(NoFloat);
         style->setDisplay(equivalentBlockDisplay(style->display(), style->isFloating(), !m_useQuirksModeStyles));
     }
 }
 
 }