Revert "Revert "[css3-text] Implement text-decoration property shorthand""

Source/core/css/CSSParser-in.cpp

Index: Source/core/css/CSSParser-in.cpp
diff --git a/Source/core/css/CSSParser-in.cpp b/Source/core/css/CSSParser-in.cpp
index a25c6de9a71087df3afaf4d2f7f287334f9d2339..4ff8f2b5bd3f9e254626ee20656f7325da7d4362 100644
--- a/Source/core/css/CSSParser-in.cpp
+++ b/Source/core/css/CSSParser-in.cpp
@@ -2113,6 +2113,12 @@ bool CSSParser::parseValue(CSSPropertyID propId, bool important)
     }
 
     case CSSPropertyTextDecoration:
+        // Fall through 'text-decoration-line' parsing if CSS 3 Text Decoration
+        // is disabled to match CSS 2.1 rules for parsing 'text-decoration'.
+        if (RuntimeEnabledFeatures::css3TextDecorationsEnabled()) {
+            // [ <text-decoration-line> || <text-decoration-style> || <text-decoration-color> ] | inherit
+            return parseShorthand(CSSPropertyTextDecoration, textDecorationShorthand(), important);
+        }
     case CSSPropertyWebkitTextDecorationsInEffect:
     case CSSPropertyTextDecorationLine:
         // none | [ underline || overline || line-through || blink ] | inherit
@@ -9013,7 +9019,8 @@ bool CSSParser::parseTextDecoration(CSSPropertyID propId, bool important)
             value = m_valueList->next();
     }
 
-    if (list->length() && isValid) {
+    // Values are either valid or in shorthand scope.
+    if (list->length() && (isValid || inShorthand())) {
         addTextDecorationProperty(propId, list.release(), important);
         return true;
     }