Simplify watched selector handling and remove remnants of user stylesheets

Source/core/css/parser/BisonCSSParser-in.cpp

Index: Source/core/css/parser/BisonCSSParser-in.cpp
diff --git a/Source/core/css/parser/BisonCSSParser-in.cpp b/Source/core/css/parser/BisonCSSParser-in.cpp
index 1406ba9d6b3a127cfbeba937b9b550b7ed353166..79d2a7e3c57498d7325d992987572f70d78deba9 100644
--- a/Source/core/css/parser/BisonCSSParser-in.cpp
+++ b/Source/core/css/parser/BisonCSSParser-in.cpp
@@ -490,9 +490,6 @@ bool isValidKeywordPropertyAndValue(CSSPropertyID propertyId, CSSValueID valueID
         return valueID == CSSValueHorizontal || valueID == CSSValueVertical || valueID == CSSValueInlineAxis || valueID == CSSValueBlockAxis;
     case CSSPropertyWebkitBoxPack:
         return valueID == CSSValueStart || valueID == CSSValueEnd || valueID == CSSValueCenter || valueID == CSSValueJustify;
-    case CSSPropertyInternalCallback:
-        // This property is only injected programmatically, not parsed from stylesheets.
-        return false;
     case CSSPropertyColumnFill:
         return RuntimeEnabledFeatures::regionBasedColumnsEnabled()
             && (valueID == CSSValueAuto || valueID == CSSValueBalance);
@@ -621,7 +618,6 @@ bool isKeywordPropertyID(CSSPropertyID propertyId)
     case CSSPropertyWebkitBoxLines:
     case CSSPropertyWebkitBoxOrient:
     case CSSPropertyWebkitBoxPack:
-    case CSSPropertyInternalCallback:
     case CSSPropertyWebkitColumnBreakAfter:
     case CSSPropertyWebkitColumnBreakBefore:
     case CSSPropertyWebkitColumnBreakInside: