Make CSSRuleSourceData use the CSSRule Type enum

Source/core/css/StyleSheetContents.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2012 Apple Inc. 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 445 matching lines @@
         case StyleRuleBase::FontFace:
             if (toStyleRuleFontFace(rule)->properties().hasFailedOrCanceledSubresources())
                 return true;
             break;
         case StyleRuleBase::Media:
             if (childRulesHaveFailedOrCanceledSubresources(toStyleRuleMedia(rule)->childRules()))
                 return true;
             break;
         case StyleRuleBase::Import:
         case StyleRuleBase::Namespace:
+        case StyleRuleBase::Unknown:
             ASSERT_NOT_REACHED();
         case StyleRuleBase::Page:
         case StyleRuleBase::Keyframes:
         case StyleRuleBase::Keyframe:
         case StyleRuleBase::Supports:
         case StyleRuleBase::Viewport:
             break;
         }
     }
     return false;
@@ skipping 176 matching lines @@
     visitor->trace(m_ownerRule);
     visitor->trace(m_importRules);
     visitor->trace(m_childRules);
     visitor->trace(m_loadingClients);
     visitor->trace(m_completedClients);
     visitor->trace(m_ruleSet);
 #endif
 }
 
 }