Clamp shape-margin to zero

Source/core/css/PropertySetCSSStyleDeclaration.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Research In Motion Limited. 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 199 matching lines @@
 void AbstractPropertySetCSSStyleDeclaration::setProperty(const String& propertyName, const String& value, const String& priority, ExceptionState& exceptionState)
 {
     CSSPropertyID propertyID = cssPropertyID(propertyName);
     if (!propertyID)
         return;
 
     bool important = equalIgnoringCase(priority, "important");
     if (!important && !priority.isEmpty())
         return;
 
+    propertySet().setForceOverride(true);
     setPropertyInternal(propertyID, value, important, exceptionState);
+    propertySet().setForceOverride(false);
 }
 
 String AbstractPropertySetCSSStyleDeclaration::removeProperty(const String& propertyName, ExceptionState& exceptionState)
 {
     StyleAttributeMutationScope mutationScope(this);
     CSSPropertyID propertyID = cssPropertyID(propertyName);
     if (!propertyID)
         return String();
 
     willMutate();
@@ skipping 156 matching lines @@
 }
 #endif
 
 DEFINE_TRACE(InlineCSSStyleDeclaration)
 {
     visitor->trace(m_parentElement);
     AbstractPropertySetCSSStyleDeclaration::trace(visitor);
 }
 
 } // namespace blink