First past at removing writing mode.

sky/engine/core/css/parser/BisonCSSParser-in.cpp

Index: sky/engine/core/css/parser/BisonCSSParser-in.cpp
diff --git a/sky/engine/core/css/parser/BisonCSSParser-in.cpp b/sky/engine/core/css/parser/BisonCSSParser-in.cpp
index 9b662905324d972dafbaecc95cafb16fae2624fb..f888bdef9b771a24156d62327a891b9c1b2bd497 100644
--- a/sky/engine/core/css/parser/BisonCSSParser-in.cpp
+++ b/sky/engine/core/css/parser/BisonCSSParser-in.cpp
@@ -510,8 +510,6 @@ bool isValidKeywordPropertyAndValue(CSSPropertyID propertyId, CSSValueID valueID
         return valueID == CSSValueReadOnly || valueID == CSSValueReadWrite || valueID == CSSValueReadWritePlaintextOnly;
     case CSSPropertyWebkitUserSelect: // auto | none | text | all
         return valueID == CSSValueAuto || valueID == CSSValueNone || valueID == CSSValueText || valueID == CSSValueAll;
-    case CSSPropertyWebkitWritingMode:
-        return valueID >= CSSValueHorizontalTb && valueID <= CSSValueHorizontalBt;
     case CSSPropertyWhiteSpace: // normal | pre | nowrap
         return valueID == CSSValueNormal || valueID == CSSValuePre || valueID == CSSValuePreWrap || valueID == CSSValuePreLine || valueID == CSSValueNowrap;
     case CSSPropertyWordBreak: // normal | break-all | break-word (this is a custom extension)
@@ -597,7 +595,6 @@ bool isKeywordPropertyID(CSSPropertyID propertyId)
     case CSSPropertyWebkitUserDrag:
     case CSSPropertyWebkitUserModify:
     case CSSPropertyWebkitUserSelect:
-    case CSSPropertyWebkitWritingMode:
     case CSSPropertyWhiteSpace:
     case CSSPropertyWordBreak:
     case CSSPropertyWordWrap: