Remove CSSRule.UNKNOWN_RULE and CSSUnknownRule interface

Source/core/css/CSSRule.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * (C) 2002-2003 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2002, 2006, 2007, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Andreas Kling (kling@webkit.org)
  *
  * 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 23 matching lines @@
 class CSSRuleList;
 class CSSStyleSheet;
 class StyleRuleBase;
 
 class CSSRule : public RefCountedWillBeGarbageCollectedFinalized<CSSRule>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
     virtual ~CSSRule() { }
 
     enum Type {
-        UNKNOWN_RULE,
-        STYLE_RULE,
-        CHARSET_RULE,
-        IMPORT_RULE,
-        MEDIA_RULE,
-        FONT_FACE_RULE,
-        PAGE_RULE,
-        // 7 was VARIABLES_RULE; we now match other browsers with 7 as
-        // KEYFRAMES_RULE:
-        // <https://bugs.webkit.org/show_bug.cgi?id=71293>.
-        KEYFRAMES_RULE,
+        STYLE_RULE = 1,
+        CHARSET_RULE = 2,
+        IMPORT_RULE = 3,
+        MEDIA_RULE = 4,
+        FONT_FACE_RULE = 5,
+        PAGE_RULE = 6,
+        KEYFRAMES_RULE = 7,
         WEBKIT_KEYFRAMES_RULE = KEYFRAMES_RULE,
-        KEYFRAME_RULE,
+        KEYFRAME_RULE = 8,
         WEBKIT_KEYFRAME_RULE = KEYFRAME_RULE,
         SUPPORTS_RULE = 12,
         VIEWPORT_RULE = 15,
     };
 
     virtual Type type() const = 0;
     virtual String cssText() const = 0;
     virtual void reattach(StyleRuleBase*) = 0;
 
     virtual CSSRuleList* cssRules() const { return 0; }
@@ skipping 47 matching lines @@
         CSSStyleSheet* m_parentStyleSheet;
     };
 };
 
 #define DEFINE_CSS_RULE_TYPE_CASTS(ToType, TYPE_NAME) \
     DEFINE_TYPE_CASTS(ToType, CSSRule, rule, rule->type() == CSSRule::TYPE_NAME, rule.type() == CSSRule::TYPE_NAME)
 
 } // namespace blink
 
 #endif // CSSRule_h