Make CSSRuleSourceData use the CSSRule Type enum

Source/core/css/invalidation/StyleSheetInvalidationAnalysis.cpp

 /*
  * Copyright (C) 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 109 matching lines @@
     case StyleRule::FontFace: // If the fonts aren't in use, we could avoid recalc.
     case StyleRule::Supports: // If we evaluated the supports-clause we could avoid recalc.
     case StyleRule::Viewport: // If the viewport doesn't match, we could avoid recalcing.
     case StyleRule::Keyframes: // If the animation doesn't match an element, we could avoid recalc.
         return true;
 
     // These should all be impossible to reach:
     case StyleRule::Keyframe:
     case StyleRule::Namespace:
     case StyleRule::Style:
+    case StyleRule::Unknown:
         break;
     }
     ASSERT_NOT_REACHED();
     return true;
 }
 
 void StyleSheetInvalidationAnalysis::analyzeStyleSheet(StyleSheetContents* styleSheetContents)
 {
     // Updating the style on the shadow DOM for image fallback content can bring us here when imports
     // are still getting loaded in the main document. Just need to exit early as we will return here
@@ skipping 68 matching lines @@
             element->setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::StyleSheetChange));
             // The whole subtree is now invalidated, we can skip to the next sibling.
             element = ElementTraversal::nextSkippingChildren(*element);
             continue;
         }
         element = ElementTraversal::next(*element);
     }
 }
 
 }