Make CSSRuleSourceData use the CSSRule Type enum

Source/core/css/StyleRule.cpp

Index: Source/core/css/StyleRule.cpp
diff --git a/Source/core/css/StyleRule.cpp b/Source/core/css/StyleRule.cpp
index e2c96835803fdfcddeb765cdeb2d02d5ec79038d..79b0da33c2f3ce56c46e36124a610e44dce847fa 100644
--- a/Source/core/css/StyleRule.cpp
+++ b/Source/core/css/StyleRule.cpp
@@ -86,6 +86,8 @@ DEFINE_TRACE(StyleRuleBase)
     case Viewport:
         toStyleRuleViewport(this)->traceAfterDispatch(visitor);
         return;
+    case Unknown:
+        break;
     }
     ASSERT_NOT_REACHED();
 }
@@ -123,6 +125,8 @@ void StyleRuleBase::finalizeGarbageCollectedObject()
     case Viewport:
         toStyleRuleViewport(this)->~StyleRuleViewport();
         return;
+    case Unknown:
+        return;
     }
     ASSERT_NOT_REACHED();
 }
@@ -160,6 +164,8 @@ void StyleRuleBase::destroy()
     case Viewport:
         delete toStyleRuleViewport(this);
         return;
+    case Unknown:
+        return;
     }
     ASSERT_NOT_REACHED();
 }
@@ -187,6 +193,7 @@ PassRefPtrWillBeRawPtr<StyleRuleBase> StyleRuleBase::copy() const
         return toStyleRuleViewport(this)->copy();
     case Keyframe:
     case Namespace:
+    case Unknown:
         ASSERT_NOT_REACHED();
         return nullptr;
     }
@@ -225,6 +232,7 @@ PassRefPtrWillBeRawPtr<CSSRule> StyleRuleBase::createCSSOMWrapper(CSSStyleSheet*
         break;
     case Keyframe:
     case Namespace:
+    case Unknown:
         ASSERT_NOT_REACHED();
         return nullptr;
     }