Optimize for horizontal writing mode

Source/core/css/resolver/StyleBuilderCustom.cpp

Index: Source/core/css/resolver/StyleBuilderCustom.cpp
diff --git a/Source/core/css/resolver/StyleBuilderCustom.cpp b/Source/core/css/resolver/StyleBuilderCustom.cpp
index 61f9469503e9409c0ba3b885b951b06d94bc637f..cbe06133e0c63989da7c34a0eb04f9ceaa962c05 100644
--- a/Source/core/css/resolver/StyleBuilderCustom.cpp
+++ b/Source/core/css/resolver/StyleBuilderCustom.cpp
@@ -897,8 +897,12 @@ void StyleBuilderFunctions::applyValueCSSPropertyWebkitAppRegion(StyleResolverSt
 
 void StyleBuilderFunctions::applyValueCSSPropertyWebkitWritingMode(StyleResolverState& state, CSSValue* value)
 {
-    if (value->isPrimitiveValue())
-        state.setWritingMode(*toCSSPrimitiveValue(value));
+    if (value->isPrimitiveValue()) {
+        CSSPrimitiveValue* primitiveValue = toCSSPrimitiveValue(value);
+        state.setWritingMode(*primitiveValue);
+        if (!isHorizontalWritingMode(*primitiveValue))
+            state.document().setHasVerticalWritingMode(true);
+    }
 
     // FIXME: It is not ok to modify document state while applying style.
     if (state.element() && state.element() == state.document().documentElement())